Content:

GI – Geosciences Instrumentation & Data Systems

GI1.1 – Open session on geoscience instrumentation and methods

EGU21-1107 | vPICO presentations | GI1.1

An improved analytical method for Re-Os isotope analysis and its application to GSJ geochemical reference materials, JCu-1 and JZn-1

Mizuki Ogasawara, Junichiro Ohta, Mizuki Ishida, Moei Yano, Kazutaka Yasukawa, and Yasuhiro Kato

The Re-Os isotope system is an effective tool in geological studies, especially in radiometric dating. Since both Re and Os are highly siderophile and chalcophile elements, they tend to be concentrated in various sulfide minerals. Therefore, the Re-Os geochronology has been employed for direct age determination of sulfide mineralization [1, 2]. However, conventional analytical methods for the Re-Os dating are complex and consume much time and cost.

Here we present an improved analytical method for Re-Os in sulfides combined with acid digestion using HClO4 [3] and sparging introduction of Os [4]. In our method, 0.4 g of powdered sulfide was digested by 1 mL of HClO4 in addition to 4 mL of inverse aqua regia in Carius tube, and then the Re and Os isotope ratios were measured by MC-ICP-MS. We applied this method to the GSJ geochemical reference materials JCu-1 (copper ore from Kamaishi mine, northeastern Japan) and JZn-1 (zinc ore from Kamioka mine, central Japan). The Re-Os concentrations of JCu-1 and JZn-1 were 255-280 ppt and 4622-4828 ppt for Re, and 39.7-41.7 ppt and 21.7-30.0 ppt for Os, respectively. Furthermore, the analytical results (Re-Os concentrations, 187Os/188Os, and 187Re/188Os) of separated chalcopyrite from Kamaishi mine showed good agreements with those by the conventional method digesting 0.5 g of sample by 10 mL of inverse aqua regia and measured with N-TIMS.

The new method, using less total volume of acids for sample digestion, enables MC-ICP-MS analysis of sulfides with relatively lower Re and Os concentrations. In addition, for Os isotopes, a sparging method using MC-ICP-MS [4] can be utilized as a simplified analytical procedure. This simplified and improved method may be useful for dating a wider range of sulfide deposits efficiently.

 

1: Nozaki, T. et al. (2013) Sci. Rep. 3, 1889.

2: Kato, Y. et al. (2009) Earth Planet. Sci. Lett., 278, 40-49.

3: Gao, B. et al. (2019) Microchem. J. 150, 104165.

4: Nozaki, T. et al. (2012) Geostand. Geoanal. Res. 36, 131-148.

How to cite: Ogasawara, M., Ohta, J., Ishida, M., Yano, M., Yasukawa, K., and Kato, Y.: An improved analytical method for Re-Os isotope analysis and its application to GSJ geochemical reference materials, JCu-1 and JZn-1, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1107, https://doi.org/10.5194/egusphere-egu21-1107, 2021.

EGU21-1523 | vPICO presentations | GI1.1

From Point Clouds to Surfaces: Overview on a Case Study

Kacper Pluta and Gisela Domej

The process of transforming point cloud data into high-quality meshes or CAD objects is, in general, not a trivial task. Many problems, such as holes, enclosed pockets, or small tunnels, can occur during the surface reconstruction process, even if the point cloud is of excellent quality. These issues are often difficult to resolve automatically and may require detailed manual adjustments. Nevertheless, in this work, we present a semi-automatic pipeline that requires minimal user-provided input and still allows for high-quality surface reconstruction. Moreover, the presented pipeline can be successfully used by non-specialists and only relies commonly available tools.

Our pipeline consists of the following main steps: First, a normal field over the point cloud is estimated, and Screened Poisson Surface Reconstruction is applied to obtain the initial mesh. At this stage, the reconstructed mesh usually contains holes, small tunnels, and excess parts – i.e., surface parts that do not correspond to the point cloud geometry. In the next step, we apply morphological and geometrical filtering in order to resolve the problems mentioned before. Some fine details are also removed during the filtration process; however, we show how these can be restored – without reintroducing the problems – using a distance guided projection. In the last step, the filtered mesh is re-meshed to obtain a high-quality triangular mesh, which – if needed – can be converted to a CAD object represented by a small number of quadrangular NURBS patches.

Our workflow is designed for a point cloud recorded by a laser scanner inside one of seven artificially carved caves resembling chapels with several niches and passages to the outside of a sandstone hill slope in Georgia. We note that we have not tested the approach for other data. Nevertheless, we believe that a similar pipeline can be applied for other types of point cloud data, – e.g., natural caves or mining shafts, geotechnical constructions, rock cliffs, geo-archeological sites, etc. This workflow was created independently, it is not part of a funded project and does not advertise particular software. The case study's point cloud data was used by courtesy of the Dipartimento di Scienze dell'Ambiente e della Terra of the Università degli Studi di Milano–Bicocca.

How to cite: Pluta, K. and Domej, G.: From Point Clouds to Surfaces: Overview on a Case Study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1523, https://doi.org/10.5194/egusphere-egu21-1523, 2021.

EGU21-2510 | vPICO presentations | GI1.1

Correcting position of delayed on-the-go field measurements by optimizing nearest neighbor statistics

Alfonso Gonzalez Jimenez, Yakov Pachepsky, José Luis Gómez Flores, Mario Ramos Rodríguez, and Karl Vanderlinden

On-the-go field measurements of soil and plant characteristics, including yield, are commonplace in current Precision Agriculture applications. Yet, such measurements can be affected by positional inaccuracies that result from equipment configuration or operation characteristics (e.g. GPS antenna position with respect to sensor position) and delays in the data transmission, reception or logging. The resulting time and position lags cause a misfit between the measurements and their attributed GPS position.

In order to compensate for this effect a simple coordinate translation along the measurement direction is proposed, depending on the local velocity and a field- and measurement configuration-specific time lag, which is estimated by minimizing the average absolute difference between the nearest neighbors. The correction procedure is demonstrated using electromagnetic induction data with different spatial configurations and by comparing
variograms for corrected and non-corrected data.


Best results are obtained when overlapping measurements are available, obtained in opposite driving directions, while the worst results are found when no overlapping measurements exist or only those corresponding to headland turns. Further improvements in the nearest neighbor search algorithm, e.g. by imposing the search in adjacent measurement swaths are discussed. The results are valid beyond motorized soil sensing applications.

Acknowledgement
This work is funded by the Spanish State Agency for Research through grant PID2019-104136RR-C21 and by IFAPA/FEDER through grant AVA2019.018.

How to cite: Gonzalez Jimenez, A., Pachepsky, Y., Gómez Flores, J. L., Ramos Rodríguez, M., and Vanderlinden, K.: Correcting position of delayed on-the-go field measurements by optimizing nearest neighbor statistics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2510, https://doi.org/10.5194/egusphere-egu21-2510, 2021.

EGU21-4112 | vPICO presentations | GI1.1

A dual-tube sampling technique for snowpack studies

Remi Dallmayr, Johannes Freitag, Maria Hörhold, Thomas Laepple, Johannes Lemburg, Damiano Della Lunga, and Frank Wilhelms

The validity of any glaciological paleo proxy used to interpret climate records is based on the level of understanding of their transfer from the atmosphere into the ice sheet and their recording in the snowpack. Large spatial noise in snow properties is observed, as the wind constantly redistributes the deposited snow at the surface routed by the local topography. To increase the signal-to-noise ratio and getting a representative estimate of snow properties with respect to the high spatial variability, a large number of snow profiles is needed. However, the classical way of obtaining profiles via snow-pits is time and energy-consuming, and thus unfavourable for large surface sampling programs. In response, we present a dual-tube technique to sample the upper metre of the snowpack at a variable depth resolution with high efficiency. The developed device is robust and avoids contact with the samples by exhibiting two tubes attached alongside each other in order to (1) contain the snow core sample and (2) to access the bottom of the sample, respectively. We demonstrate the performance of the technique through two case studies in East Antarctica where we analysed the variability of water isotopes at a 100 m and 5 km spatial scales.

How to cite: Dallmayr, R., Freitag, J., Hörhold, M., Laepple, T., Lemburg, J., Della Lunga, D., and Wilhelms, F.: A dual-tube sampling technique for snowpack studies, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4112, https://doi.org/10.5194/egusphere-egu21-4112, 2021.

EGU21-6055 | vPICO presentations | GI1.1

RS41 GRUAN Data Product Version 1 (RS41-GDP.1) - Reference Radiosonde Data for the Troposphere and Lower Stratosphere

Michael Sommer, Christoph von Rohden, Tzvetan Simeonov, and Ruud Dirksen

One of the main goals of the GCOS Reference Upper Air Network (GRUAN) is to perform reference observations of profiles of atmospheric temperature, humidity and wind for monitoring climate change. Two essential criteria for establishing a reference observation are measurement-traceability and the availability of measurement uncertainties. Radiosoundings have proven valuable in providing in-situ profiles of temperature, humidity, pressure and wind at unmatched vertical resolution. Data products from commercial radiosondes often rely on black-box or proprietary algorithms, which are not disclosed to the scientific user. Furthermore, long-term time-series from these products are frequently hampered by changes in the hardware and/or the data processing.

The GRUAN data products (GDP’s) comply with the above-mentioned criteria for a reference product. Correction algorithms are open-source and well documented and the data include vertically resolved best estimates of the uncertainties. Another major advantage of a GRUAN data product is that it includes the radiosonde’s raw measurement data, which allows for reprocessing when new or improved corrections become available. Currently, GDP’s are available for the Vaisala RS92 and Meisei RS-11G radiosondes. Data products for additional radiosonde models, as well as for other measurement techniques are in the making. The GDP’s are used to determine trends, constrain and calibrate data from more spatially‐comprehensive observing systems (including satellites and current radiosonde networks), and provide appropriate data for studying atmospheric processes.

This presentation introduces the GRUAN processing of Vaisala RS41 radiosoundings, the correction algorithms that are applied, and the derivation of the vertically resolved uncertainty estimates. Well-known, dominant error sources for the RS41 profiles are related to solar radiation, causing a temperature error, and time-lag of the humidity sensor at low temperatures. The corrections for these error sources are based on dedicated experiments that were performed at Lindenberg observatory to measure the response of the RS41 temperature sensor to solar irradiance and to determine the time-lag of the humidity sensor at temperatures down to -70 °C. The RS41-GDP.1 is planned to become available in 2021. The majority of the 30, globally distributed, GRUAN sites employ the RS41, and its predecessor the RS92 before, establishing a continuous data record of more than 10 years of reference climate observations.

How to cite: Sommer, M., von Rohden, C., Simeonov, T., and Dirksen, R.: RS41 GRUAN Data Product Version 1 (RS41-GDP.1) - Reference Radiosonde Data for the Troposphere and Lower Stratosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6055, https://doi.org/10.5194/egusphere-egu21-6055, 2021.

EGU21-6646 | vPICO presentations | GI1.1

Low-cost sensor network in remote alpine environments

Federico Dallo, Daniele Zannoni, Jacopo Gabrieli, Paolo Cristofanelli, Francescopiero Calzolari, Fabrizio de Blasi, Andrea Spolaor, Dario Battistel, Rachele Lodi, Warren R. L. Cairns, Ann Mari Fjæraa, Paolo Bonasoni, Fred Bauman, and Carlo Barbante

We present the results obtained using an original open-source low-cost sensor (LCS) system developed to measure tropospheric O3 in a remote high altitude alpine site. We conducted our study at the Col Margherita Observatory (2543 m a.s.l.), a World Meteorological Organization Global Atmosphere Watch Regional Station (WIGOS Id: 0-380-0-MRG), located in the Italian Eastern Alps. The sensing system mounts three equivalent commercial low-cost sensors that have been calibrated using a laboratory standard (Thermo 49iPS), referenced to the Standard Reference Photometer #15 calibration scale by the WMO, before field deployment. Intra and inter-comparison between sensors and reference (Thermo 49c) have been conducted for six months from May to December 2018. The sensor’s dependence on the environmental meteorological variables has been considered and discussed. The evaluation of the analytical performances of this sensing system provides a limit of detection < 5 ppb, limit of quantitation < 17 ppb, linear dynamic range up to 250 ppb, intra-Pearson correlation coefficient (PCC) up to 0.96, inter-PCC > 0.8, bias > 3.5 ppb and ±8.5 at 95% of confidence. Thanks to the first implementation of an LCS System in an alpine site, we demonstrated how it is possible to obtain valuable data from a low-cost instrument in a remote harsh environment. This opens new perspectives for the adoption of a low-cost sensor network in atmospheric sciences. We further present our recent experience using LoRa to integrate the sensing system into a low-power wide-area network (LPWAN). We developed an end-node and a gateway, designing PCBs derived from the Arduino Mega, optimizing their power consumption and equipping them with batteries, a proper solar panel or wind turbine to ensure their autonomy while collecting environmental ozone and meteorological (T, RH, WS, WD) data. We drafted the communication software to send compressed data from end-nodes to gateways. The gateways are part of an openVPN with the main server located in Venice. The server also provides a postgreSQL database and a R-shiny web application for data visualization and manipulation. To enhance redundancy, the local data are also synchronized to a cloud database. In the next years, thanks to the Marie Skłodowska-Curie grant PIONEER, we will exploit our experiences to provide a comprehensive low-cost wireless sensor network to characterize transport of polluted air masses and provide long term climate data collection in support of the state-of-the-art instrumentation and established networks in remote alpine areas.

Bibliography

Dallo F. et al.: Calibration and assessment of electrochemical low-cost sensors in remote alpine harsh environments, Atmospheric Measurement Techniques, amt-2020-483. In review

Acknowledgements. This work was part of the Arctic Field Grant O3NET project, funded by the Research Council of Norway. The work received financial support by the National Project of Interest Next-Data (MIUR). The exploitation of the LoRa technology was performed with the ITIS "Max Planck" through the Remote Observatory SYstem (ROSY) "Alternanza scuola-lavoro" project. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 844526

How to cite: Dallo, F., Zannoni, D., Gabrieli, J., Cristofanelli, P., Calzolari, F., de Blasi, F., Spolaor, A., Battistel, D., Lodi, R., Cairns, W. R. L., Fjæraa, A. M., Bonasoni, P., Bauman, F., and Barbante, C.: Low-cost sensor network in remote alpine environments, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6646, https://doi.org/10.5194/egusphere-egu21-6646, 2021.

EGU21-6960 | vPICO presentations | GI1.1

Core-CT:  A MATLAB application for the quantitative analysis of sediment and coral cores from X-ray computed tomography (CT) 

Yu Ting Yan, Stephen Chua, Thomas DeCarlo, Philipp Kempf, Kyle Morgan, and Adam Switzer

X-ray computed tomography (CT) is a non-destructive imaging technique that provides three-dimensional (3D) visualisation and high-resolution quantitative data in the form of CT numbers. CT numbers are derived as a function of the X-ray energy, effective atomic number and density of the sample. The sensitivity of the CT number to changes in material density allows it to successfully identify facies changes within sediment cores by detecting downcore shifts in sediment properties, and quantify skeletal linear extension rates and the volume of internal voids from biological erosion of coral cores. Here we present two algorithms to analyse CT scan images specific to geoscience research packaged within an open source MATLAB application (Core-CT). The first algorithm facilitates the computation of representative CT numbers from a user-defined region of interest to identify boundaries of density change (e.g. sedimentary facies, laminations, coral growth bands). The second algorithm enables the segmentation of regions with major density contrast (e.g. internal void space or biogenic material) and the geometric measurements of these irregularities. The versatility of Core-CT for geoscience applications is then demonstrated by utilising CT scans from a range of environmental settings comprising both sediment (Lake Huelde, Chile and Kallang River Basin, Singapore) and coral cores (Thuwal region of Red Sea, Saudi Arabia). Analysis of sediment cores show the capabilities of Core-CT to: 1) locate tsunami deposits from lacustrine sediments, 2) provide rapid and detailed measurement of varved sediments, and 3) identify sedimentary facies from an unsplit shallow marine sediment core. Analysis of coral cores allow us to successfully measure skeletal linear extension from annual growth bands, and provide volumetric quantification and 3D visualisation of internal bioerosion. Core-CT is an accessible, multi-use MATLAB based program that is freely available at GitHub  (https://github.com/yuting-yan/Core-CT).

 

How to cite: Yan, Y. T., Chua, S., DeCarlo, T., Kempf, P., Morgan, K., and Switzer, A.: Core-CT:  A MATLAB application for the quantitative analysis of sediment and coral cores from X-ray computed tomography (CT) , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6960, https://doi.org/10.5194/egusphere-egu21-6960, 2021.

EGU21-7984 | vPICO presentations | GI1.1

Innovative software solutions for subsea positionings

Pierre-Yves Morvan and Gary Bagot

Improving operational efficiency is a recurring challenge for subsea operations. Throughout the life of a field, from construction up to decommissioning, several subsea vehicles will be deployed to cover various tasks to perform underwater observations. An ROV or AUV assigned to a specific task will require multiple positioning sensors (LBL, USBL, INS…) to complete its mission. Defining the “good enough” subsea positioning strategy, i.e. to ensure a minimum accuracy without compromise on safety, can be a complex exercise. For instance, an overestimation of the LBL transponders required will directly induce vessel time and finally costly operations. On the other hand, a certain level of positioning redundancy may be requested for a vehicle operating close to a subsea asset in production.

To ease the design and monitoring of a subsea vehicle navigation, iXblue has developed an integrated solution. Not only has the company broadened its product range with the new intelligent Canopus LBL Transponder and the new generation Ramses transceiver, but with Delph Subsea Positioning Software, iXblue now provides a complete integrated solution for subsea positioning that goes a step further by bringing significant efficiency. Divided in 4 modules (LBL Array Planning, Navigation Simulation, Operations, DelphINS) with an intuitive user interface, Delph Subsea Positioning (DSP) is an integrated software suite for the preparation, the operation and the post-processing of iXblue positioning devices (USBL, LBL and INS).

How to cite: Morvan, P.-Y. and Bagot, G.: Innovative software solutions for subsea positionings, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7984, https://doi.org/10.5194/egusphere-egu21-7984, 2021.

EGU21-8624 | vPICO presentations | GI1.1

Investigations based on biaxial tiltmeter array and uniaxial hydrostatic levelling system at the Mont Terri rock laboratory

Dorothee Rebscher, Yves Guglielmi, Inma Gutierrez, Edi Meier, and Senecio Schefer

In order to enable investigations and further comprehensive understanding of dynamical processes, it is clear one has to identify all relevant parameters and aim to record them all under best conditions concerning e.g. resolution, coverage in space, and in many cases on a multitude of scales in time. Obviously, it is also difficult to satisfy all these constrains in full. Especially scientific long-term observations often suffer the lack of necessary lasting commitment; secure funding, continual high quality maintenance, protected environment, or sufficient planning stability. Fortunately, the Swiss Mont Terri rock laboratory, with its history of now 25 years of forefront scientific expertise, a long-standing fruitful cooperation formed by the partners of the consortium and in consequence thereof state-of-the-art results obtained through 100 completed individual experiments and 45 additional experiments actually ongoing, ensures the conditions listed above.

Based on this favorable prospect, a now growing tiltmeter array is established at the underground laboratory. The instruments are embedded in several multidisciplinary experiments, dedicated to numerous, different scientific questions. Starting in April 2019, the first two platform tiltmeters became operational. Less than two years later, ten biaxial instruments are quasi-continuously monitoring deformation at various locations within the galleries and niches at Mont Terri. The envisioned, increasing spatial coverage of the network will facilitate geodetic observations of the underground rock laboratory as a whole and of its subregions as well.

Already in September 2012, a 50 m long hydrostatic levelling system (HLS) was installed along a gallery in the underground laboratory to detect displacements across an active geological fault zone. The combination of both, i.e. the uniaxial, integral deformations data provided by HLS together with the array of biaxial, point measurements acquired by the tiltmeters offers a unique concerted opportunity to achieve detailed deformation data in a large underground rock laboratory and to survey the associated dynamical processes occurring on timeframes covering seconds to decades.

How to cite: Rebscher, D., Guglielmi, Y., Gutierrez, I., Meier, E., and Schefer, S.: Investigations based on biaxial tiltmeter array and uniaxial hydrostatic levelling system at the Mont Terri rock laboratory, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8624, https://doi.org/10.5194/egusphere-egu21-8624, 2021.

EGU21-9287 | vPICO presentations | GI1.1

A Novel Approach for a better exploitation of a 3D seismic on a development field 

Nasrine Medjdouba, Zahia Benaissa, and Sabiha Annou

The main hydrocarbon-bearing reservoirover the study area is the lower Triassic Argilo-Gréseux reservoir. The Triassic sand is deposited as fluvial channels and overbank sands with a thickness ranging from 10 to 20 m, lying unconformably on the Paleozoic formations. Lateral and vertical distribution of the sand bodies is challenging which makes their mapping very difficult andnearly impossible with conventional seismic analysis. 

In order to better define the optimum drilling targets, the seismic attribute analysis and reservoir characterization process were performed targeting suchthin reservoir level, analysis of available two seismic vintages of PSTM cubes as well as post and pre stack inversion results were carried out.The combination of various attributes analysis (RMS amplitude, Spectral decomposition, variance, etc.) along with seismic inversion results has helped to clearly identify the channelized feature and its delineation on various horizon slices and geobodies, the results were reviewed and calibrated with reservoir properties at well location and showed remarkable correlation.

Ten development wells have been successfully drilledbased on the seismic analysis study, confirming the efficiency of seismic attribute analysis to predicted channel body geometry.

Keywords: Channel, Attributes, Amplitude, Inversion, Fluvial reservoir.

How to cite: Medjdouba, N., Benaissa, Z., and Annou, S.: A Novel Approach for a better exploitation of a 3D seismic on a development field , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9287, https://doi.org/10.5194/egusphere-egu21-9287, 2021.

EGU21-9793 | vPICO presentations | GI1.1

Digital zenith camera VESTA and its applications

Inese Varna, Ansis Zarins, and Augusts Rubans

The portable digital zenith camera (DZC) VESTA (VErtical by STArs) determines the deflection of vertical (DoV) components as the difference between the direction to the ellipsoidal zenith (calculated from reference star observations, fixing precise time moment and site coordinates) and the direction of the plumb line, which is determined with a sensitive tiltmeter. DZC VESTA was developed at the University of Latvia and has been used extensively for the determination of the Latvian quasi-geoid model since 2016. The typical accuracy of VESTA is ~0.1 arc second.

Unlike levelling, relative gravimetry or GNSS measurements, the method used by the zenith camera determines DoV directly, allowing validation of data from other geodetic techniques, for example, DZCs are used for geoid slope validations.

Currently, the focus is on further improving the accuracy of the digital zenith camera. Investigation of the limiting factors to achieve the highest accuracy for applied and scientific applications includes:

  • testing the digital zenith camera in different environments to investigate and mitigate the phenomenon of anomalous refraction at zenith; anomalous refraction is the main limiting factor of ground-based astrometric observation’s precision, as it causes irregular angular displacements of the observed stars. The proposed tests include more thorough long-term observations to search for the anomalous refraction properties at multiple test sites (such as near the seacoast, on a hill slope, in a forest, in an open field, covering a wide range of environmental conditions) under different weather conditions. Simultaneous observations with several adjacent DZCs would be an efficient method to distinguish instrument-related variations from changes in the measured quantity itself and to find the spatial properties of the anomalous refraction effects.
  • performing accuracy analysis in a permanent test site to esti­mate the spatial and temporal properties of the measured DoV values. Astrogeodetic determination of DoVs is an absolute observational technique, and any undetected systematic errors remain in the data. Various instrumental settings will be tested during the observations.

However, digital zenith cameras are not limited to geodetic applications; there are other ideas for possible fields of application:

  • research focusing on applications in a geological survey;
  • monitoring of changes in mass distribution in the Earth's crust in case of active tectonic movements.

These areas of geoscience would benefit from an additional measurement technique that complements the traditional method of relative gravimetry.

This research is funded by PostDoc Latvia grant contract No. 1.1.1.2/VIAA/4/20/666.

How to cite: Varna, I., Zarins, A., and Rubans, A.: Digital zenith camera VESTA and its applications, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9793, https://doi.org/10.5194/egusphere-egu21-9793, 2021.

EGU21-9848 | vPICO presentations | GI1.1

The tilt and strainmeter network of NE Italy: multi-decadal observations of crustal deformation as ground truth for DinSAR.

Carla Braitenberg, Alberto Pastorutti, Barbara Grillo, and Marco Bartola

Decade-long series of tilt- and strain-meter observations in NE Italy allow monitoring the crustal deformation from short transient to long-term phenomena. These recordings, some of them started in 1960, are generated by sources spanning a wide spectrum of spatial scales, such as sudden underground flooding due to extreme rainfall [1, 2], years-long fluid diffusion transients due to fault behavior [3], the free oscillation arising from megathrust earthquakes (e.g. Chile 1960, Sumatra 2004, Tohoku 2011).
The instrumental sites lie on karst formations, in an area of continental collision and active seismicity, the northeastern portion of the Adria microplate, where the south-directed thrusts of the Alpine system merge with the NW-SE transpressive regime of the External Dinarides. Measurements include the ongoing interseismic strain accumulation processes, including the peculiar observation of episodic disturbances and southward tilting in the three years preceding the 1976 Mw6.4 Friuli earthquake [4].

The channel systems of Karst hydrology, which undergo complete flooding and overpressure buildup in extremely short time spans (e.g. near-simultaneous flooding over a distance of 30 km) result in observable surface deformation and a change in the gravity field. Tilt time series allow to extract and model this type of hydrology-forced uplift and associated deformation [2,5].

Tilt- and strain-meters allow for accuracy and precision in measuring crustal deformation, to a level which space-borne geodesy cannot provide. The main drawback, however, is that only point measurements are provided, in locations where stations could be set up.
On the other hand, the thousands of points on the surface that DInSAR can provide are affected by coarser accuracy and influenced by atmospheric effects - resulting in LoS displacements uncorrelated to the actual surface deformations. We aim at enabling the transfer of knowledge from tilt- and strain-meters observations to DInSAR-derived data, thus allowing a first assessment of ground-truth constrained displacement models.

[1] Braitenberg C. (2018). The deforming and rotating Earth - A review of the 18th International Symposium on Geodynamics and Earth Tide, Trieste 2016 , Geodesy and Geodynamics, 187-196, doi::10.1016/j.geog.2018.03.003

[2] Braitenberg C., Pivetta T., Barbolla D. F., Gabrovsek F., Devoti R., Nagy I. (2019). Terrain uplift due to natural hydrologic overpressure in karstic conduits. Scientific Reports, 9:3934, 1-10, doi.:10.1038/s41598-019-38814-1

[3] Rossi, G., Fabris, P. & Zuliani, D. Overpressure and Fluid Diffusion Causing Non-hydrological Transient GNSS Displacements. Pure Appl. Geophys. 175, 1869–1888 (2018). https://doi.org/10.1007/s00024-017-1712-x

[4] Dragoni M., Bonafede M., and Boschi E. (1985). On the interpretation of slow ground deformation precursory to the 1976 Friuli earthquake. Pure and Applied Geophysics 122, 781–792. doi:10.1007/978-3-0348-6245-5_3

[5] Grillo B., Braitenberg C., Nagy I., Devoti R., Zuliani D., Fabris P. (2018). Cansiglio Karst-Plateau: 10 years of geodetic-hydrological observations in seismically active northeast Italy. Pure and Applied Geophysics, 175, 5, 1765-1781, doi:10.1007/s00024-018-1860-7.

 

How to cite: Braitenberg, C., Pastorutti, A., Grillo, B., and Bartola, M.: The tilt and strainmeter network of NE Italy: multi-decadal observations of crustal deformation as ground truth for DinSAR., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9848, https://doi.org/10.5194/egusphere-egu21-9848, 2021.

EGU21-9974 | vPICO presentations | GI1.1

Spectral X-ray computed micro tomography: a tool for 3-dimensional chemical imaging

Jonathan Sittner, Margarita Merkulova, Jose Ricardo da Assuncao Godinho, Axel Renno, Veerle Cnudde, Marijn Boone, Thomas De Schryver, Denis Van Loo, Antti Roine, Jussi Liipo, Bradley Martin Guy, and Stijn Dewaele

Image-based analytical tools in geosciences are indispensable for the characterization of minerals, but most of them are limited to the surface of a polished plane in a sample and lack 3D information. X-ray micro computed tomography (micro CT) provides the missing 3D information of the microstructures inside samples. However, a major drawback of micro CT in the characterization of minerals is the lack of chemical information that makes mineral classification challenging.

Spectral X-ray micro computed tomography (Sp-CT) is a new and evolving tool in different applications such as medicine, security, material science, and geology. This non-destructive method uses a multi-pixel photon-counting detector (PCD) such as cadmium telluride (CdTe) in combination with a conventional CT scanner (TESCAN CoreTOM) to image a sample and detect its transmitted polychromatic X-ray spectrum. Based on the spectrum, elements in a sample can be identified by an increase in attenuation at specific K-edge energies. Therefore, chemically different particles can be distinguished inside a sample from a single CT scan. The method is able to distinguish elements with K-edges in the range from 25 to 160 keV, which applies to elements with Z > 48 (Sittner et al., 2020).

We present results from various sample materials. Different pure elements and element oxides were measured to compare the position of theoretical and measured K-edge energies. All measured K-edge energies are slightly above the theoretical value, but based on the results a correction algorithm could be developed. Furthermore, different monazite grains were investigated, which can be divided into two groups with respect to the content of different RE elements on the basis of the spectrum: La-Ce-rich and La-Ce-poor. In addition, samples from the Au-U Witwatersrand Supergroup demonstrate the potential applications of Sp-CT for geological samples. We measured different drill core samples from the Kalkoenkrans Reef at the Welkom Gold field. Sp-CT can distinguish gold, uraninite and galena grains based on their K-edge energies in the drill core without preparation.

Sittner, J., Godinho, J. R. A., Renno, A. D., Cnudde, V., Boone, M., De Schryver, T., Van Loo, D., Merkulova, M., Roine, A., & Liipo, J. (2020). Spectral X-ray computed micro tomography: 3-dimensional chemical imaging. X-Ray Spectrometry, September, 1–14.

How to cite: Sittner, J., Merkulova, M., Godinho, J. R. D. A., Renno, A., Cnudde, V., Boone, M., De Schryver, T., Van Loo, D., Roine, A., Liipo, J., Guy, B. M., and Dewaele, S.: Spectral X-ray computed micro tomography: a tool for 3-dimensional chemical imaging, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9974, https://doi.org/10.5194/egusphere-egu21-9974, 2021.

EGU21-11168 | vPICO presentations | GI1.1

Spectral method for processing hydromagnetic survey data at shallow depths

Kirill Kuznetsov, Kiryukhina Elena, Bulychev Andrey, and Lygin Ivan

Magnetic surveys are commonly used for solving variety of geotechnical and geological challenges in offshore areas, jointly with a set of other geophysical methods. The most popular technique employed is hydromagnetic surveying with towed magnetometers. One of the most significant challenges encountered during processing of the magnetic data is related to temporal variations of the Earth's magnetic field. Accounting for diurnal magnetic field variations is often done by carrying out differential hydromagnetic surveys, a technique developed in the 1980-s. It is based on simultaneous measurements of the magnetic field using two sensors towed behind the vessel with a given separation. This technique allows to calculate along-course gradient which is free of magnetic field temporal variations. This measurement system resembles a gradiometer, with the distance between two sensors being referred to as the base of the gradiometer. It is possible to calculate anomalous magnetic field by integrating obtained magnetic field gradient. Studies have shown that accuracy of its reconstruction decreases with increasing base of the gradiometer. This becomes most significant when distance between the sensors and sources of magnetic field anomalies is small. This situation occur when the survey area is located in shallow water (i.e. for shallow marine, river or lake surveys).

An approach for deriving magnetic anomalies and accounting for diurnal variations in differential hydromagnetic surveys based on the frequency (spectral) representation of the measurements was proposed in 1987 [Melikhov, 1987]. This approach utilizes the fact that it is possible to reconstruct the spectrum of magnetic field anomalies along the vessel course from the spectra of measured signals from the first S1(ω) and second S2(ω) sensors. Assuming that the sensors are located at the same depth, it can be achieved via the following transform:

where ω - spatial frequency, l - base of the gradiometer, and i - imaginary unit. Assuming that at a single moment in time magnetic field variations equally affect both sensors, resulting Fourier spectrum T(ω) will correspond the spectrum of anomalous magnetic field, free of the magnetic variations. It should be noted that, similar to the along-course gradient integration approach, anomalous magnetic field is restored to a certain accuracy level.

Estimates made on model examples showed that accuracy of the field reconstruction using this method is comparable to the accuracy levels of modern marine magnetic surveys (±1-3 nT). It could be noted that for gradiometer bases comparable or larger than depths to magnetic anomaly sources, errors of the field reconstruction are significantly lower for the spectral transformation-based approach compared to along-course gradient integration.

References:

Melikhov V.R., Bulychev A.A., Shamaro A.M. Spectral method for solving the problem of separating the stationary and variable components of the geomagnetic field in hydromagnetic gradiometric surveys // Electromagnetic research. - Moscow. IZMIRAN, 1987. - P. 97-109. (in Russian)

 

How to cite: Kuznetsov, K., Elena, K., Andrey, B., and Ivan, L.: Spectral method for processing hydromagnetic survey data at shallow depths, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11168, https://doi.org/10.5194/egusphere-egu21-11168, 2021.

EGU21-12116 | vPICO presentations | GI1.1

Improvement of high resolution measurements of neodymium isotope compositions to reconstruct past ocean circulation

Eva M. Rückert, Julius Förstel, and Norbert Frank

Palaeoceanographic studies of ocean circulations are crucial for understanding the ocean´s impact on the Earth´s climate system. Circulation patterns and the provenance of water masses can be detected from temporal variations of the neodymium isotopic composition (εNd) of authigenic neodymium, preserved in deep sea sediment.

Inductively coupled plasma source mass spectrometry allows for the precise and accurate determination of εNd-values of samples and reference material.

Here, we reevaluate the mass spectrometric measurement protocol and instrument setting with respect to precision and accuracy defined by neodymium standards.

The shape of the ion beam plays a crucial role, which is manifested in the result that an optimal adjustment of the beam shaping quadrupoles can increase precision by a factor of 4.

In addition, the optimal standard neodymium concentration level is roughly 50 ppb yielding uncertainties of the mean of repeated measurements as low as 0.07 ε units whereas 5 times lower concentrations yield 10 times higher uncertainties.

The statistical nature of precision is further demonstrated through an uncertainty inversely proportional to the square root of N measurements. As a consequence, with an increase from 30 to 80 consecutive measurements precision was improved by a factor of 1.22.

Taking all evaluated aspects into account, precision and accuracy of standards and thus sediment samples can be strongly improved, hence contributing to a better comprehension of past ocean circulation, where neodymium isotope gradients are small.

How to cite: Rückert, E. M., Förstel, J., and Frank, N.: Improvement of high resolution measurements of neodymium isotope compositions to reconstruct past ocean circulation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12116, https://doi.org/10.5194/egusphere-egu21-12116, 2021.

EGU21-12735 | vPICO presentations | GI1.1

Intercomparison of the Vaisala RS92 and RS41 Radiosonde GRUAN Data Products (GDP) in the Troposphere and Lower Stratosphere

Tzvetan Simeonov, Ruud Dirksen, Christoph von Rohden, and Michael Sommer

The GCOS Reference Upper Air Network (GRUAN) consists of 30 globally distributed measurement sites that provide reference observations of essential climate variables such as temperature and water vapour for climate monitoring. At these sites, radiosondes provide in-situ profiles of temperature, humidity and pressure at high vertical resolution. However, data products from commercial radiosondes often rely on black-box or proprietary algorithms, which are not disclosed to the scientific user. Furthermore, long-term time-series from these products are frequently hampered by changes in the hardware and/or the data processing. Therefore, GRUAN data products (GDP) are developed, that employ open-source and well-documented corrections to the measured data, thereby complying with the requirements for reference data, which include measurement traceability and the availability of measurement uncertainties. The GRUAN data processing is applied to the raw measurement data of temperature, humidity, pressure, altitude, and wind, and includes corrections of errors from known sources, such as for example solar radiation error for temperature and sensor time lag for humidity measurements. The vertically resolved uncertainty estimates include the uncertainty of the applied corrections and the calibration uncertainty of the sensors.

A substantial number of GRUAN sites employ the Vaisala RS41 radiosonde, and its predecessor, the RS92, before that. This large-scale change of instrumentation poses a special challenge to the network, and great care is taken to characterize the differences between these instruments in order to prevent inhomogeneities in the data records. As part of this effort, the GRUAN data products for both radiosonde types are compared. In this study we used data from approximately 1000 RS92+RS41 twin-soundings (two sondes on a rig attached to one balloon) that were performed at 11 GRUAN sites, covering the main climate zones.

The first analysis shows that daytime temperature differences in the stratosphere increase steadily with altitude, with RS92-GDP up to 0.5 K warmer than RS41-GDP above 25 km. In addition, at daytime the RS41-GDP is 0.2 K warmer than the manufacturer-processed RS41-EDT product above 15 km. Analysis of the humidity profiles shows a slight moist bias of the RS41 compared to the RS92 for both GDP and manufacturer-processed data. Differences between the RS41-EDT and GDP humidity products are most pronounced in the upper troposphere - lower stratosphere region and are attributed to the time lagcorrection. The analysis of the temperature differences will be refined by investigating the influence of the solar radiation in conjunction with sonde orientation and ventilation. Furthermore, the uncertainty of the humidity data will be assessed by comparing with coincident measurements of the water vapor profile by the Cryogenic Frostpoint Hygrometer (CFH).

Key words: Radiosonde, RS41, RS92, humidity, temperature, uncertainty, GRUAN, troposphere, lower stratosphere

How to cite: Simeonov, T., Dirksen, R., von Rohden, C., and Sommer, M.: Intercomparison of the Vaisala RS92 and RS41 Radiosonde GRUAN Data Products (GDP) in the Troposphere and Lower Stratosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12735, https://doi.org/10.5194/egusphere-egu21-12735, 2021.

EGU21-12850 | vPICO presentations | GI1.1

Long-term recordings at the FSU Jena Geodynamic Observatory Moxa (Thuringia, central Germany)

Nina Kukowski, Ronny Stolz, Theo Scholtes, Cornelius Schwarze, and Andreas Goepel

The remote location of the Geodynamic Observatory Moxa of Friedrich-Schiller University Jena, about 30 km south of Jena in the Thuringian slate mountains, results in very low ambient noise and thus very good conditions for long-term geophysical observations, which are further improved, as many sensors are installed in the subsurface in galleries or in boreholes.

So far, the focus of Moxa observatory has been on observing transients signals of deformation and fluid movements in the subsurface. This is accomplished by sensors like a superconducting gravimeter CD-034, three laser strain meters measuring nano-strain along three galleries in north-south, east-west and NW-SE directions, or borehole tiltmeters. Further, information on fluid flow is gained from downhole temperature measurements employing an optical fiber. These sensors are complemented by a climate station and two shallow drill-holes, one of which has been fully cored, which in addition to the temperature times series provide information on water level and rock physical properties. Near surface geophysical profiling using e.g. electrical resistivity tomography has led to a good knowledge of the structurally complex subsurface of the observatory.

Recently, a node for the Global Network of Optical Magnetometers for Exotic physics (GNOME) has been installed in the temperature-stabilized room at Moxa observatory close to the superconducting gravimeter. The GNOME is a world-spanning collaboration employing optically pumped magneto­meters (OPM) to search for space-time correlated transient signatures heralding exotic physics beyond the Standard Model. GNOME is sensitive to prominent classes of dark-matter scenarios, e.g., axion or axion-like particles forming macroscopic structures in the Universe. The installation in close vicinity to the superconducting gravimeter ensures well-controlled and -monitored ambient conditions such as temperature, air pressure and especially vibrations, allowing improved vetoing of false-positive detection events in the Moxa GNOME node.

Here, we focus on introducing Moxa Observatory’s sensor systems with an emphasis of actual sensor configurations and further on highlighting how various information on fluid flow coming from the specific sensors lead to an improved understanding of the direction and magnitude of subsurface fluid flow.

How to cite: Kukowski, N., Stolz, R., Scholtes, T., Schwarze, C., and Goepel, A.: Long-term recordings at the FSU Jena Geodynamic Observatory Moxa (Thuringia, central Germany), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12850, https://doi.org/10.5194/egusphere-egu21-12850, 2021.

EGU21-13053 | vPICO presentations | GI1.1

Joint ESA and NASA Imaging Spectrometer Airborne Campaign to Support CHIME and SBG

Robert Green, Michael Rast, Michael Schaepman, Andreas Hueni, and Michael Eastwood

In 2018 a joint ESA and NASA airborne campaign was orchestrated with the University of Zurich to advance cooperation and harmonization of algorithms and products from imaging spectrometer measurements.  This effort was intended to benefit the future candidate European Copernicus Hyperspectral Imaging Mission for the Environment (CHIME) and NASA Surface Biology and Geology mission. For this campaign, the Airborne Visible/Infrared Imaging Spectrometer Next Generation was deployed from May to July 2018.  Twenty-four study sites were measured across Germany, Italy, and Switzerland.  All measurements were rapidly calibrated, atmospherically corrected, and made available to NASA and ESA investigators.  An expanded 2021 campaign is now planned with goals to: 1) further test and evaluate new state-of-the-art science algorithms: atmospheric correction, etc; 2)  grow international science collaboration in support of ESA CHIME and NASA SBG; 3) test/demonstrate calibration, validation, and uncertainty quantification approaches;  4) collect strategic cross-comparison under flights of space missions: DESIS, PRISMA, Sentinels, etc.  In this paper, we present an overview of the key results from the 2018 campaign and plans for the 2021 campaign.

 

How to cite: Green, R., Rast, M., Schaepman, M., Hueni, A., and Eastwood, M.: Joint ESA and NASA Imaging Spectrometer Airborne Campaign to Support CHIME and SBG, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13053, https://doi.org/10.5194/egusphere-egu21-13053, 2021.

EGU21-13138 | vPICO presentations | GI1.1

Challenges and opportunities from large volume, multi-offset Ground Penetrating Radar data

Dimitrios Angelis, Craig Warren, Nectaria Diamanti, James Martin, and Peter Annan

The most frequently used survey mode for acquiring Ground Penetrating Radar (GPR) data is common offset (CO) – where a single transmitter and receiver pair move along a survey line at a constant (offset) separation distance. This allows rapid and dense data acquisition, and therefore high-resolution large-scale investigations, to be carried out with relative ease, and at relatively low cost. However, it has long been known that multi-offset survey methods, such as common mid-point (CMP) and wide-angle reflection-refraction (WARR), can offer many benefits over CO: detailed subsurface EM wave velocity models; enhanced reflection sections with higher signal-to-noise ratio (SNR); the potential to adapt well-established advanced seismic processing schemes for GPR data [1-2].

Despite the advantages of multi-offset GPR data, these methods have seen limited adoption as, in the past, they required significantly more time, effort, and hence cost, to collect. However, recent advances in GPR hardware, particularly in timing and control technology, have enabled the development of multi-concurrent sampling receiver GPR systems such as the “WARR Machine” manufactured by Sensors & Software Inc. [3-4]. These newly developed GPR systems have the potential to provide all the aforementioned benefits with considerably less effort and therefore reduced survey cost, as they allow for the fast acquisition of multi-offset WARR soundings.

In this work, we look at the challenges and opportunities from collecting and processing multi-offset GPR data. We demonstrate a processing workflow that combines standard GPR processing approaches, with methods adapted from seismic processing, as well as our own algorithms. This processing framework has been implemented into a GUI-based software written in MATLAB [5], and has been tested using both synthetic [6] and real multi-offset GPR data. Some of the specific challenges with multi-offset GPR that we investigate are time zero misalignments, CMP balancing, velocity analysis, and automated velocity picking. We show how addressing these issues can result in improved velocity analysis, and ultimately in improved subsurface velocity models, and stacked sections.

References

[1] Ursin, B., 1983. Review of elastic and electromagnetic wave propagation in horizontally layered media. Geophysics, 48(8), pp.1063-1081.

[2] Carcione, J. and Cavallini, F., 1995. On the acoustic-electromagnetic analogy. Wave Motion, 21(2), 149-162.

[3] Annan, A. P., and Jackson, S., 2017. The WARR machine. 2017 9th International Workshop on Advanced Ground Penetrating Radar (IWAGPR).

[4] Diamanti, N., Elliott, J., Jackson, R. and Annan, A. P., 2018, The WARR Machine: System Design, Implementation and Data: Journal of Environmental & Engineering Geophysics, 23, pp.469-487.

[5] Angelis, D., Warren, C. and Diamanti, N., 2020. A software toolset for processing and visualization of single and multi-offset GPR data. 18th International Conference on Ground Penetrating Radar.

[6] Warren, C., Giannopoulos, A. and Giannakis, I., 2016. gprMax: Open source software to simulate electromagnetic wave propagation for Ground Penetrating Radar. Computer Physics Communications, 209, pp.163-170.

How to cite: Angelis, D., Warren, C., Diamanti, N., Martin, J., and Annan, P.: Challenges and opportunities from large volume, multi-offset Ground Penetrating Radar data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13138, https://doi.org/10.5194/egusphere-egu21-13138, 2021.

EGU21-13341 | vPICO presentations | GI1.1

Experiences on production - usage reasoned malfunctions & development of  X-ray tubes used in science and their effects on sediment measurements

Dursun Acar, Namık Çagatay, Ş. Can Genç, K. Kadir Eriş, Demet Biltekin, and Nurettin Yakupoğlu

Surface fractures at the filament of X-ray tube increase more with metal fatique or wrong cooling  and heating processes. Fractured filament continue to work as repeating open circuit positions in random times with  turning fully conductive state in short time. We are explaining how open circuit flashes at the filament providing wrong measurement results. Their low voltage electric circuit conductive problems  repeat in milliseconds periods. At  the results, it gives the impression of healthy measurement values. Because that the measured sample absorbs photonic energy and direct it to neighbouring elements in continuous element  electron scattering  circulations , by the way that delayed secondary electron energy scatters hide all electron supply extinctions on the semi broken flament wire and indirect counts  continue by the detector from coming reflection energy. ( real counts are not from exact beam  target of sample surface during energy deprivations , and it is impossible to understand that the measurement is inaccurate because it causes similarity as discrete element counts in sedimentation layers ).  Filament voltage arcs do not warn machine with error reporting systems until to whole ruptured filament touch to anode walls or their far displaced edges of 2 broken filament positioning. Erroneous records take their place in the world of science if the lithology was not followed. We collected faulty measurement data from our experiences for indicate when and  how possible to facing such as events.

For eliminate  explained reasons at above , the tubes must be gently heated and  cooled. Excessive cooling or heating of the tubes or oxid placement and leakeage  at gasget contacts reduces the surface contact areas of the insilators with the corrosion by  condensing water around the rubber insulation gasgets , it causes cooling liquid leakage or increasing humidity at the tube housing block via following serial failures of HV unit such as increasing amounts of the broken tube events. During the replacement of insulating gasgets, enough care should be taken for gasket contact points as oiling  them with  silicone grease as a form of the thin film. High responsibility must be with continuous  result control  and reference correlations on the scientific sample. With this way we can eliminate possible  negative results by malfunctions on measurements.

How to cite: Acar, D., Çagatay, N., Genç, Ş. C., Eriş, K. K., Biltekin, D., and Yakupoğlu, N.: Experiences on production - usage reasoned malfunctions & development of  X-ray tubes used in science and their effects on sediment measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13341, https://doi.org/10.5194/egusphere-egu21-13341, 2021.

EGU21-14085 | vPICO presentations | GI1.1

Overview of the Airborne Phased Array Radar Observing Simulator

Wen-Chau Lee, Jothiram Vivekanandan, Scott Ellis, Kevin Manning, George Bryan, Lou Lussier, Vanda Grubišić, and Bradley Klotz

The proposed airborne phased array radar (APAR) system consists of four removable, dual-polarized, C-band AESAs (Active Electronic Scanning Array) strategically located on the fuselage of the NSF/NCAR C-130. Conceptually, the radar system is divided into the front-end, the backend, and aircraft-specific section with the front-end primarily consisting of AESAs and the signal processor is in the backend. The aircraft specific section includes a power system and a GPS antenna.

As part of the risk reduction of the APAR development, the APAR Observing Simulator (AOS) system has been developed to provide simulated APAR data collection sampled from a C-130 flying by/through realistic numerical weather simulations of high-impact weather events. Given that APAR is designed to extend beyond capabilities of the existing airborne tail Doppler radars (e.g., NOAA TDRs and the retired NSF/NCAR ELDORA), a verification of signal processing software and algorithms is needed before the radar is physically built to ensure that the signal processing software infrastructure can handle high data rates and complicated, multiplex scanning that will be part of normal APAR operations.  Furthermore, several algorithms that will need to ingest large amounts of APAR data at very high rates are under development, including dual-Doppler wind synthesis, radar reflectivity attenuation correction, rain rate estimation, and hydrometeor classification. These algorithms need to be tested and verified before the implementation. 

The AOS will also serve as a planning tool for future Principal Investigators (PIs) who will use it to design and test different flight and scanning strategies based on simulated storms to yield the best scientific outcomes before their field deployment takes place. This will enable better understanding of trade-offs among various sampling regimes/strategies during the planning and enhance future field programs' efficiency and effectiveness.

How to cite: Lee, W.-C., Vivekanandan, J., Ellis, S., Manning, K., Bryan, G., Lussier, L., Grubišić, V., and Klotz, B.: Overview of the Airborne Phased Array Radar Observing Simulator, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14085, https://doi.org/10.5194/egusphere-egu21-14085, 2021.

EGU21-15640 | vPICO presentations | GI1.1

Optical frequency dissemination via fiber networks: The Clock Network Services (CLONETS) project and potential applications in the geosciences

Juergen Kusche and the CLOck NETwork Services - Design Study (CLONETS DS) Team

Precise measurement of time and frequency has been instrumental in the development of modern geosciences. It has enabled us to quantify many observations, including plate motion, the variations of Earth rotation, and modern-day sea level rise.

Over the past decade, European National Metrology Institutes (NMIs), together with National Research and Education Networks (NRENs) and partners from universities and research institutes have pioneered the dissemination of ultra-stable optical frequency and timing signals via optical fibers. Initially started as proof-of-concept experiments, this technology has matured to aim for a paradigm change: making precise time and frequency signals available to the wider scientific community and thereby enabling new research avenues.

The CLOck NETwork Services Design Study (CLONETS-DS) is a research and innovation action intended to facilitate the vision of a sustainable, pan-European optical fiber network for precise time and frequency reference dissemination.

Here, we will present the envisioned technology, its performance parameters, and discuss potential applications, requirements and limitations for geophysical applications, for example in geodesy (chronometric levelling, gravity field observation), seismology, and very-long-baseline interferometry (VLBI).

How to cite: Kusche, J. and the CLOck NETwork Services - Design Study (CLONETS DS) Team: Optical frequency dissemination via fiber networks: The Clock Network Services (CLONETS) project and potential applications in the geosciences, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15640, https://doi.org/10.5194/egusphere-egu21-15640, 2021.

EGU21-16275 | vPICO presentations | GI1.1

Development and implementation of a low-cost long-period telluric recorder for deep Earth electrical investigations

Tarek Arafa-Hamed, Hossam Marzouk, Michael Becken, Ahmed Lethy, and Hatem Odah
Magnetotelluric loggers are key instruments for deep geophysical studies of crust and mantle. However, conducting a large-scale survey requires the implementation of a series of magnetotelluric instruments to complete the measurements in an efficient time. The main efforts and costs of a magnetotelluric survey are devoted to magnetic recordings. Therefore, using a compination of magnetotelluric stations along with parallel tellurics recorders can significantly reduce the time and costs needed to complete a regional survey. Based on this motivation, we present the construction, implementation and case studies of a long period telluric recorder (LPTR). The telluric recorder is based on a 24 bit ADC with a multiplexer that enables 2 differential channels devoted to the Ex and Ey telluric components. The multiplexer is adjusted to provide 1sample per second from each channel that corresponds to 2Hz sampling rate at the ADC. The multiplexing at this rate reduces the ADC efficient resolution to 20 bit. As the full measuring range is +/- 1.25V the least significant bit LSB is about 2.4 micro V. The output of the ADC is transferred via USB to a mini PC for time stamping and saving. The time of each record is provided from a GPS with accuracy of 1 ms. The LPTR is connected to the ground using a Cu-CuSo4 nonpolarizable electrodes. The electrodes are specially constructed to provide good and longterm connection to the ground in arid environments. The LPTR has been tested throughout several field implementations in Egypt. The setup for contiuous telluric acquisition is realized in Moghra, Dakhla, Farafra and in Fayoum. These locations covers a variety of northern and southern Egypt as well as western desert and Nile valy. During the test implementations the recorder is put to run parallel to an ADU07-e magnetotelluric system for 1-3 days then for 2-4 months to be compared and integrated with the magnetic observatories at Fayoum and Abo Simble. Both observatories are running MAGSON fluxgate magnetometers at a sampling rate of 1 Hz. The resultant data showed that the LPTR synchronizes with the ADU07-e at periods from 5s and with the magnetic observatory data at periods 25s. This indicates an efficient low-cost system that can be used for deep Earth resistivity investigations. A case study of 2-4 months of continuous telluric recordings that have been processed with magnetic observatories data provided impedances for periods up to 42000 seconds. The results are 1D modeled for depths of more than 800KM. A comparison between the obtained 1D MT model and global Earth-models (LITHO1) based on seismological data shows a quite good matching at the deep interfaces like upper crust, middle crust and lower crust. The delineation of seismic discontinuities at 410 KM and 680 KM shows corresponding clear change in resistivity at 410 KM and then at 700 KM as well.

How to cite: Arafa-Hamed, T., Marzouk, H., Becken, M., Lethy, A., and Odah, H.: Development and implementation of a low-cost long-period telluric recorder for deep Earth electrical investigations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16275, https://doi.org/10.5194/egusphere-egu21-16275, 2021.

GI1.2 – New frontiers of multiscale monitoring, analysis, modeling and decisional support (DSS) of environmental systems

EGU21-11023 | vPICO presentations | GI1.2 | Highlight

Modelling ground deformation in Tenerife (Canary Islands) during 2003-2010

Monika Przeor, Luca D'Auria, Susi Pepe, and Pietro Tizzani

Tenerife is the biggest island of the Canaries and one of the most active from the volcanological point of view. The island is geologically complex, and its main volcano-tectonic features are three volcanic rifts and the composite volcanic complex of Teide-Las Cañadas. The latter is located in the central part of the island at the intersection of Tenerife principal rifts. Teide volcano, with its 3718 m of elevation constitutes the most prominent topographical feature of the island. Being a densely populated active volcanic island, Tenerife is characterised by a high volcanic risk. For this reason, the island requires an advanced and efficient volcano monitoring system. Among the geophysical parameters that could be useful to forecast an oncoming volcanic eruption, the ground deformation is relevant for detecting the approach of magma to the surface.

This study aim is to analyse the ground deformation in the surroundings of the Teide-Las Cañadas complex.  For this purpose, we studied the ground deformation of Tenerife by using a set of Synthetic Aperture Radar (SAR) images acquired between 2003 and 2010 by the ENVISAT ASAR sensor and processed through a DInSAR-SBAS technique. The DInSAR SBAS time series revealed a ground deformation in the central part of the island, coinciding with the Teide volcano. A similar deformation was already evidenced by Fernández et al. (2009) from 2004 to 2005.

We investigated the source of this ground deformation by applying the statistical tool of Independent Component Analysis (ICA) to the dataset. ICA allowed separating the spatial patterns of deformation into four components. We attributed three of them to an actual ground deformation, while the fourth seems to be only related to the noise component of data. The first component (ICA1) displays a spatial pattern localised in Teide volcano neighbourhoods and consists of a ground uplift of few centimetres. The deformation associated with this component starts in 2005 and persists along the rest of the time series. The second component (ICA2) of the ground deformation is localised in the South/South-West part of Las Cañadas rim while the third component (ICA3) is localised to the East of Teide volcano. We performed inverse modelling to analyse the source of the ground deformation related to ICA1 to retrieve the location, the geometry and the temporal evolution of this source. The inversion was based on analytical models of ground deformation as well as on Finite-Element-Modelling. The result showed that the ground deformation is associated with a shallow sill-like structure, located beneath Teide volcano, possibly reflecting a hydrothermal reservoir. The knowledge of this source geometry could be of significant interest to better understand ground deformation data of possible future volcanic crisis. 

How to cite: Przeor, M., D'Auria, L., Pepe, S., and Tizzani, P.: Modelling ground deformation in Tenerife (Canary Islands) during 2003-2010, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11023, https://doi.org/10.5194/egusphere-egu21-11023, 2021.

EGU21-9881 | vPICO presentations | GI1.2

Non-uniqueness in the inversion of volcano deformation data: change of volume or change of position?

Erika Ronchin, Raffaele Castaldo, Susi Pepe, Pietro Tizzani, Giuseppe Solaro, and Maurizio Battaglia

The detailed spatial and temporal information of surface deformation detected during volcanic unrest by InSAR images suggests a degree of complexity of volcanic systems (e.g., source geometries and distribution of material properties) that cannot be correctly represented by simple models of a pressure source embedded in an elastic, homogeneous, isotropic half-space.

The inversion of deformation data, performed for the characterization of the source of deformation, is based on the model we choose to represent the volcanic system. Therefore the quality of the chosen model influences the source size and its temporal changes estimated through the inversion, and thus their interpretation. In fact, our assumptions about geometries and/or magma and rock properties affect the estimations of changes in magma volumes and reservoir pressure. To obtain a more reliable interpretation of surface signals, it is thus paramount to have more realistic models, where the distribution of material properties is constrained by multiple data sets, with greater flexibility in the definition of sources in space and time.

Assuming we could invert InSAR data with models that can deal with a complex and arbitrarily shaped deformation source, how unique could this solution be? How much could we say about the evolution of the deformation source over time? Furthermore, how much information about the spatial complexity of the source and its evolution in space and time would be missed?

To answer these questions, we characterize the deformation source from the inversion of InSAR data based on a finite element method (FEM) forward model without an a-priori source geometry. The deformation source is bound by estimating the strength of an amorphous cluster of deformation sources distributed over a grid. This uses the principle of superposition already applied to point or cuboid volume elements, embedded in a homogeneous half-space. Also, the numerical model integrates the cluster-source with a heterogeneous distribution of material properties and the topography.

In our study, we quantify the ambiguity in the estimation of arbitrary geometries of sources of deformation composed by clusters of Finite Element Method unit sources distributed over a grid. The regularized least-squares solutions of the steady-state PDEs inverse model are obtained using a COMSOL Multiphysics-based routine. Through the inversion of the InSAR time series of the unrest at Uturuncu volcano (Bolivia), we quantify the ability of the employed cluster-source approach to identify the changes of deformation sources in time. 

This research is financed by an individual fellowship of the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 793811.

How to cite: Ronchin, E., Castaldo, R., Pepe, S., Tizzani, P., Solaro, G., and Battaglia, M.: Non-uniqueness in the inversion of volcano deformation data: change of volume or change of position?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9881, https://doi.org/10.5194/egusphere-egu21-9881, 2021.

EGU21-11104 | vPICO presentations | GI1.2

Multiscale Spatial and Temporal Analysis of the b-value in volcanic areas

Rubén García-Hernández, Luca D'Auria, José Barrancos, and German D. Padilla

Determining the b-value of the Gutenberg-Richter law is of great importance in Seismology. However, its estimate is strongly dependent upon selecting a proper temporal and spatial scale due to the multiscale nature of the seismicity. This characteristic is especially relevant in volcanoes where dense clusters of earthquakes often overlap the background seismicity and where this parameter displays a higher spatial and temporal variability.

For this reason, we devised a novel approach called MUST-B (MUltiscale Spatial and Temporal estimation of the B-value) which allows a consistent estimate of the b-value, avoiding subjective “a priori ” choices, by considering simultaneously different temporal or spatial scales. This approach also includes a consistent estimation of the completeness magnitude (Mc) and the uncertainties over both b and Mc. We applied this method to datasets in volcanic areas proving its effectiveness to analyze complex seismicity patterns and its utility in volcanic monitoring and geothermal exploration. Besides, it may provide a way to distinguish seismicity caused by tectonic faults and volcanic sources in zones where there is a mix of both of them.

We present MUST-B applications to three volcanic areas: Long Valley caldera (USA), Tenerife and El Hierro (Canary Islands). The spatial analysis of the b-value in Long Valley shows an impressive chimney-like volume characterized by high b-values which coincide with the main pathway of geothermal fluids inferred by independent studies. For Tenerife, we applied MUST-B to analyze both spatial and temporal variations. The spatial pattern shows an interesting variation between 2004-2005 and the period 2016-2020. In both cases, high b-values appear in an area that hosted increased seismicity because of seismo-volcanic crises. These high b-values are also evidenced by the temporal analysis, which shows an increase in correspondence between these two periods. For El Hierro, we analyzed the seismicity preceding the 2011 submarine eruption of Tagoro volcano using a joint spatio-temporal analysis. Results show high b-values in the area where the vent opened and a drop of this parameter just before the beginning of the eruption.

How to cite: García-Hernández, R., D'Auria, L., Barrancos, J., and Padilla, G. D.: Multiscale Spatial and Temporal Analysis of the b-value in volcanic areas, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11104, https://doi.org/10.5194/egusphere-egu21-11104, 2021.

EGU21-12143 | vPICO presentations | GI1.2

Analysis of magnetotelluric data from Las Cañadas caldera (Tenerife, Spain)

David Martínez van Dorth, Federico Di Paolo, Katarzyna Slezak, Iván Cabrera-Pérez, Perla Piña-Varas, Juanjo Ledo, Garazi Bidaurrazaga Aguirre, Lucía Sáez Gabarrón, Monika Przeor, William Hernández, Luca D'Auria, and Nemesio M. Pérez

Tenerife is the second-largest island in the Canarian archipelago with an area of 2034 km2. It consists of three ancient volcanic massifs (Anaga, Adeje and Teno) located at the edges of the island connected by rift zones to the centre of the island, in correspondence of Las Cañadas caldera. The caldera hosts the most relevant topographic element of Tenerife, the volcanic edifice of Teide – Pico Viejo. Previous studies already suggested the presence of geothermal resources inside and around the caldera. For this reason, in the present study, we have applied the magnetotelluric method (MT) in the central part of the island to better understand subsurface structures in this area.

The MT method is a useful tool successfully applied to detect conductive and resistive structures located in the subsoil. It is commonly used in volcanic areas to detect volcano-tectonic features and geothermal systems to evaluate exploitable geothermal resources. Furthermore, continuous magnetotelluric measurements can also be employed for volcanic monitoring, allowing tracking temporal changes of the resistivity because of fluid transfer processes in the volcanic system.

Between 2019 and 2020 we realised a detailed study of Las Cañadas caldera resistivity structure thought 45 magnetotelluric soundings. The instrumentation consisted of four Metronix ADU-08e, equipped with EPF-06 electrodes and MFS-06e magnetic coils, which registered electric and magnetic fields along the N-S and E-W directions. We also installed three remote stations at different times inside the caldera. Depending on the station quality, we obtained the MT response functions for periods of 0.001 – 1000 s. The dimensionality of the data has been analysed using the phase tensor.  The first preliminary results of dimensionality and strike analysis indicate a 1D/2D behaviour for the first layers which present a decreasing resistivity, evolving to a 3D behaviour from 1s and with an increase of resistivity with depth.

Furthermore, we present some results obtained by a permanent MT station to check the possibility of temporal changes in the electrical resistivity. During the time this station was recording two electrical blackouts which took place on the island. This allowed quantitatively estimating the level of anthropogenic electromagnetic noise in the recorded time series.

How to cite: Martínez van Dorth, D., Di Paolo, F., Slezak, K., Cabrera-Pérez, I., Piña-Varas, P., Ledo, J., Bidaurrazaga Aguirre, G., Sáez Gabarrón, L., Przeor, M., Hernández, W., D'Auria, L., and Pérez, N. M.: Analysis of magnetotelluric data from Las Cañadas caldera (Tenerife, Spain), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12143, https://doi.org/10.5194/egusphere-egu21-12143, 2021.

EGU21-13038 | vPICO presentations | GI1.2 | Highlight

Modeling of major environmental risks for the Kyiv city,  Ukraine from the Dnieper river waters  -  inundation of coastal areas and contamination by the radionuclides deposited in bottom sediments after the Chornobyl accident

Sergii Kivva, Mark Zheleznyak, Roman Bezhenar, Oleksandr Pylypenko, Maxim Sorokin, Andriy Demydenko, Volodymyr Kanivets, Gennady Laptev, Oleg Votsekhovich, Victoria Boyko, and Dmitri Gudkov

There are two partially linked risks to the Kyiv city associated with the Dnieper river: (A) risk of the inundation of the urban coastal areas during the extremely high floods or due to the break of the Hydropower Plant dam located upstream Kyiv, and, (B) risk of the secondary radioactive contamination of the Dnieper waters due to the intensification of the dynamics of "Chornobyl" radionuclides during high floods and man-made impacts -  dredging in Kyiv Reservoirs for navigation routes and other purposes.

The Chornobyl Nuclear Power Plant has located 130 km from Kyiv at the bank of Pripyat river, which is 20 km downstream from ChNPP inflows into the Kyiv reservoir of the Dnieper River. After the Chornobyl accident, about 5.4×1013 Bq of 137Cs and 1013 Bq of 90Sr were deposited in the bottom sediments of the Kyiv Reservoir. Nowadays, 35 years after the Chornobyl accident, the population of Kyiv still is very sensitive to the risks of secondary environmental contaminations by the “Chornobyl radionuclides”. Therefore even low levels of such risks should be carefully assessed by well-grounded methods.

The main goals of our multidisciplinary study are:

  • to develop a model/data based Decision Support System (DSS) for the assessment of both kind of the described above risks A) and B),
  • to analyze the influence of the natural hazard – extremely high river floods on the resuspension of contaminated sediments and environmental risks due to the man-made impacts – dredging, dam breaks, and others.

The components of these research and development activities are following:

  • field and laboratory studies of the contemporary contamination of the bottom sediments and biota in the Kyiv reservoir to receive the input data for the model calibration and improvement of the model structure;
  • customization for the Kyiv Reservoir and the Dnieper river at Kyiv of the 2D COASTOX model which the hydrodynamic module is based on the nonlinear shallow water equations, and the sediment/radionuclide transport model using the advection-diffusion equations with specific sink/source terms for radionuclides;
  • customization for the Kyiv Reservoir of the hydro-ecological POSEIDON model that simulates the influence of resuspension of radioactive sediments on the contamination of fishes and other hydrobionts;
  • improvement of methods for the numerical solution of model equations and algorithms based on finite volume methods for their parallelization using multiprocessor systems and graphics cards to speed up computations;
  • to create high-performance DSS with a user-friendly interface that can use GPUs to quickly predict the radiation status of surface waters and inundation of river banks in emergencies.

The DSS is installed in the Department of Hydrological Forecasting of the Ukrainian Hydrometeorological Center and is used for the quantification of the risk scenarios and analyses of the links of both risks. Due to the high computational performance, the DSS can be used for the real-time numerical predictions with the zoning of the flood risks in a case of emergency.

How to cite: Kivva, S., Zheleznyak, M., Bezhenar, R., Pylypenko, O., Sorokin, M., Demydenko, A., Kanivets, V., Laptev, G., Votsekhovich, O., Boyko, V., and Gudkov, D.: Modeling of major environmental risks for the Kyiv city,  Ukraine from the Dnieper river waters  -  inundation of coastal areas and contamination by the radionuclides deposited in bottom sediments after the Chornobyl accident, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13038, https://doi.org/10.5194/egusphere-egu21-13038, 2021.

EGU21-15403 | vPICO presentations | GI1.2

Diffuse H2 degassing studies: a useful geochemical tool for monitoring Cumbre Vieja volcano, La Palma, Canary Islands

Nemesio M. Pérez, Gladys V. Melián, Pedro A. Hernández, María Asensio-Ramos, Eleazar Padrón, Fátima Rodríguez, Mar Alonso, Alba Martín-Lorenzo, Cecilia Amonte, Luca D'Auria, José Barrancos, and Germán D. Padilla

Hydrogen (H2) is one of the most abundant trace species in volcano-hydrothermal systems and is a key participant in many redox reactions occurring in the hydrothermal reservoir gas. Although H2 can be produced in soils by N2-fixing and fertilizing bacteria, soils are considered nowadays as sinks of molecular hydrogen (Smith-Downey et al. 2006). Because of its chemical and physical characteristics, H2 generated within the crust moves rapidly and escapes to the atmosphere. These characteristics make H2 one of the best geochemical indicators of magmatic and geothermal activity at depth. Cumbre Vieja volcano (La Palma, Canary Islands) is the most active basaltic volcano in the Canaries with seven historical eruptions being Teneguía eruption (1971) the most recent one. Cumbre Vieja volcano is characterized by a main north–south rift zone 20 km long, up to 1950 m in elevation and covering an area of 220 km2 with vents located at the northwest and northeast. Cumbre Vieja does not show any visible degassing (fumaroles, etc.). For that reason, the geochemical volcano monitoring program at Cumbre Vieja volcano has been focused on soil degassing surveys.  Here we show the results of soil H2 emission surveys that have been carried out regularly since 2001. Soil gas samples were collected in about 600 sampling sites selected to obtain a homogeneous distribution at about 40 cm depth using a metallic probe and 60 cc hypodermic syringes and stored in 10 cc glass vials. H2 content was analysed later by a VARIAN CP4900 micro-GC. A simple diffusive emission mechanism was applied to compute the emission rate of H2 at each survey. Diffuse H2 emission values were used to construct spatial distribution maps by using sequential Gaussian simulation (sGs) algorithm, allowing the estimation of the emission rate from the volcano. Between 2001-2003, the average diffuse H2 emission rate was ∼2.5 kg·d−1 and an increase of this value was observed between 2013-2017 (∼16.6 kg·d−1), reaching a value of 36 kg·d−1 on June 2017, 4 month before the first recent seismic swarm in October, 2017 at Cumbre Vieja volcano. Six additional seismic swarms had occurred at Cumbre Vieja volcano (February 2018, July-August 2020; October 8-10, 2020; October 17-19, 2020, November 21, 2020 and December 23-26, 2020) and changes of diffuse H2 emission related to this unrest had been observed reaching values up to ∼70 kg·d−1. Diffuse H2 emission surveys have demonstrated to be sensitive and excellent precursors of magmatic processes occurring at depth in Cumbre Vieja. Periodic diffuse H2 emission surveys provide valuable information to improve and optimize the detection of early warning signals of volcanic unrest at Cumbre Vieja volcano.

How to cite: Pérez, N. M., Melián, G. V., Hernández, P. A., Asensio-Ramos, M., Padrón, E., Rodríguez, F., Alonso, M., Martín-Lorenzo, A., Amonte, C., D'Auria, L., Barrancos, J., and Padilla, G. D.: Diffuse H2 degassing studies: a useful geochemical tool for monitoring Cumbre Vieja volcano, La Palma, Canary Islands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15403, https://doi.org/10.5194/egusphere-egu21-15403, 2021.

EGU21-15421 | vPICO presentations | GI1.2

Changes in the thermal energy and the diffuse 3He and 4He degassing prior to the 2014-2015 eruption of Pico do Fogo volcano, Cape Verde

Mar Alonso, Nemesio M. Pérez, Eleazar Padrón, Pedro A. Hernández, Gladys V. Melián, Hirochika Sumino, Germán D. Padilla, José Barrancos, Fátima Rodríguez, Samara Dionis, María Asensio-Ramos, Cecilia Amonte, Sonia Silva, and José Manuel Pereira

Cape Verde archipelago is a cluster of several volcanic islands arranged in a westward opening horseshoe shape located in the Atlantic Ocean, between 550 and 800 km-west of the coast of Senegal (Africa). Fogo Island is located in the southwest of the archipelago, and as main feature is a 9-km-north to south wide collapse caldera opened toward the east, within Pico do Fogo volcano rises 2,829 m.a.s.l. Pico do Fogo crater has an area of 0.142 km2 and its characterized by a fumarolic field composed by low and moderate temperature fumaroles, with temperatures around 95ºC and reaching 400ºC respectively. The last eruption of Fogo volcanic system took place between November 2014 and February 2015, when four new eruptive vents were formed, and destroyed partially the villages of Portela and Bangaeira (Silva et. al., 2015) forcing the evacuation of 1,300 inhabitants. In this work we present the temporal evolution of 3He/4He isotopic ratio, 3He and 4He emission and thermal energy released data measured from March 2007 to November 2018 in the crater of Pico do Fogo. In all the studied temporal evolutions, we can observe two main increases in the above parameters, the first in early 2010, suggesting a magmatic intrusion, and the second several months before the eruption onset. We have also observed that changes in the 3He emission might be accompanied by a significant increase in thermal output if the system is in an eruptive cycle. Our results confirm 3He emission studies are highly reliable indicator of imminent volcanic eruption and constitute a powerful tool to monitor the activity of volcanic areas around the world.

Silva et al., (2015), Geophysical Research Abstracts Vol. 17, EGU2015-13378, EGU General Assembly.

How to cite: Alonso, M., Pérez, N. M., Padrón, E., Hernández, P. A., Melián, G. V., Sumino, H., Padilla, G. D., Barrancos, J., Rodríguez, F., Dionis, S., Asensio-Ramos, M., Amonte, C., Silva, S., and Pereira, J. M.: Changes in the thermal energy and the diffuse 3He and 4He degassing prior to the 2014-2015 eruption of Pico do Fogo volcano, Cape Verde, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15421, https://doi.org/10.5194/egusphere-egu21-15421, 2021.

EGU21-1698 | vPICO presentations | GI1.2

Automatic tree species classification by using field data, image analysis and deep learning techniques in riparian forests

Sarah Kentsch, Maximo Larry Lopez Caceres, and Yago Diez

Mixed forests are still little understood ecosystems. Their structure and composition are not well known and not clearly classified. In times of climate change, monitoring of forests is becoming increasingly important. Forest stands were usually researched by field work, which requires high costs and man-power. Field surveys are further only conducted in small patches of the forests, which does often not represent the whole forest. For mixed forests, usually only a dominate species is mentioned but the forests are not classified further. The greater need of better methods with high accuracies to detect and classify tree species in the forest encouraged this study.

UAVs have been proven to be an efficient tool to conduct automatic field surveys in forestry applications. These easy-to-use and cheap tools are able to gather images with a high resolution. Image processing with image analysis and deep learning techniques is an emerging part in forestry investigations. Therefore, we combined manual field surveys, image analysis and automatic classifications in our study.

The forests, we were investigating, are riparian forests in Shonai area, Japan, which are classified as mixed forests. 7 sites were chosen and field surveys were conducted. Most of the sites are located in flat areas, but 3 sites are located on slopes, where the access is difficult and field work barely possible. We imaged all sites in different seasons with UAVs and performed image analysis with computer vision and ArcGIS methods. Trees were detected and classified manually and automatically. A comparison of all applied methods was drawn, evaluated and will be provided.

Our first results are promising to characterize forests in a new dimension. We will provide detailed information about tree species composition, tree locations and forest structures. Mixed forests can be deeper analysed by maps of dominate and subdominant tree species. Area calculations for tree canopies will be highlighted for the main tree species. We will provide winter images for tree counting in heavy snowfall regions and classification accuracies of deep learning techniques.  

How to cite: Kentsch, S., Lopez Caceres, M. L., and Diez, Y.: Automatic tree species classification by using field data, image analysis and deep learning techniques in riparian forests, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1698, https://doi.org/10.5194/egusphere-egu21-1698, 2021.

EGU21-10436 | vPICO presentations | GI1.2

Contribution to the discussion on processing and measurement methodology of apatite fission-track analysis

Lucie Novakova, Raymond Jonckheere, Bastian Wauschkuhn, and Lothar Ratschbacher

Apatite fission track dating and T,t-modelling are now a well-established thermochronological instruments for investigating geological problems (Malusà and Fitzgerald, 2019). In the course of their development, complicating factors that affect the track counts and confined track lengths in geological samples were corrected for, foremost among them the crystallographic orientation of the confined track and the chemical composition of the apatite (Green et al., 1986, and subsequent papers). Methods have also been proposed to improve the confined track statistics, using 252Cf irradiation, ion irradiation, fracturing, and re-etching (Yamada et al., 1998). However, there is to date no adequate correction for the protocol used to reveal the tracks, which differs from lab to lab although all are based on nitric acid.

Recent step-etch experiments with the most used etchants show that both the duration of the etch and the temperature and concentration of the solution have non-negligible effects on the measured lengths (Sobel and Seward, 2010; Jonckheere et al., 2017 and references therein; Tamer et al., 2019). Earlier attempt to overcome these problems investigated etching for such a time that the track openings conform to a pre-determined size (Ravenhurst et al., 2003) or measuring confined tracks of a given minimum width (Yamada et al., 1993). The first method has the drawback that the widths of the host tracks and confined tracks are not directly related, whereas the second fails to consider the anisotropic width of confined tracks.

In our geological investigation of the German Naab area, we adopt a step-etch approach, measuring the c-axis angle, length, width and dip of each individual confined track after 20s and 30s immersion in 5.5 M HNO3. From the width increase we calculate the rate of widening of the track (apatite etch rate; Aslanian et al., 2021), and from that the effective etch time tE, i.e., the true duration that the confined track has been etched, equal to the immersion time minus the time needed for the etchant to reach the specific confined track. Our results show that the confined track lengths are correlated with their effective etch times. This information is used to account for etch-protocol-related differences between the induced and fossil track lengths entered in the T,t-modelling software. We envisage this will improve the accurateness and resolution of the resulting T,t-paths. We will check this against the excellent independent geological constraints that exist for the Naab region.

The research was funded by the EU/MEYS (CZ.02.2.69/0.0/0.0/19_074/0014756).

 

References

Aslanian et al., 2021. American Mineralogist. In press.

Green et al., 1986. Chemical Geology 59, 237-253.

Jonckheere et al., 2017. American Mineralogist 102, 987-996.

Malusà and Fitzgerald, 2019.  Fission-Track Thermochronology and its Application to Geology. Pp 393.

Ravenhurst et al., 2003. Canadian Journal of Earth Sciences 40, 995-1007.

Sobel and Seward, 2010. Chemical Geology 271, 59-69.

Tamer et al., 2019. American Mineralogist 104(10), 1421-1435.

Yamada et al., 1993. Chemical Geology 122, 249-258

Yamada et al., 1998. Chemical Geology 149, 99–107.

How to cite: Novakova, L., Jonckheere, R., Wauschkuhn, B., and Ratschbacher, L.: Contribution to the discussion on processing and measurement methodology of apatite fission-track analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10436, https://doi.org/10.5194/egusphere-egu21-10436, 2021.

EGU21-13772 | vPICO presentations | GI1.2

A Multi-Use Case Scientific Sensor Node

Valarie Hamilton and Andrew Moores

Nanometrics' Pegasus digitizer is the basis for a scientific grade node and is the latest development in many years of designing and building reliable seismic instruments for the scientific and monitoring community. Coupled in a grab-and-go quick deploy package with a variety of sensors enables responses to many types of events and environmental measurements. These types of systems are not only for hazards, such as earthquakes and volcanoes, but can form the basis of better tools used for critical structure and microzonation studies using ambient noise.  Pegasus takes advantage of a complete ecosystem of software, making planning, deploying and data harvesting very simple and straightforward as well as providing a dataset that includes automatically generated metadata in the form of StationXML and standard miniSEED data files.  Pegasus design criteria was based on optimal SWaP (Size, Weight and Power) and makes it unique in short to long duration deployments without swapping of units in the field, while its broad sensor compatibility enables many types of measurements and is completely compatible with the advantages of Nanometrics smart sensors.

How to cite: Hamilton, V. and Moores, A.: A Multi-Use Case Scientific Sensor Node, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13772, https://doi.org/10.5194/egusphere-egu21-13772, 2021.

GI2.1 – Data fusion, integration, correlation and advances of non-destructive testing methods and numerical developments for engineering and geosciences applications

EGU21-12125 | vPICO presentations | GI2.1

An Ontology-based approach to enable data-driven research in the field of NDT in Civil Engineering

Benjamin Moreno-Torres, Christoph Völker, and Sabine Kruschwitz

Non-destructive testing (NDT) data in civil engineering is regularly used for scientific analysis. However, there is no uniform representation of the data yet. An analysis of distributed data sets across different test objects is therefore too difficult in most cases.

To overcome this, we present an approach for an integrated data management of distributed data sets based on Semantic Web technologies. The cornerstone of this approach is an ontology, a semantic knowledge representation of our domain. This NDT-CE ontology is later populated with the data sources. Using the properties and the relationships between concepts that the ontology contains, we make these data sets meaningful also for machines. Furthermore, the ontology can be used as a central interface for database access. Non-domain data sources can be integrated by linking them with the NDT ontology, making them directly available for generic use in terms of digitization. Based on an extensive literature research, we outline the possibilities that result for NDT in civil engineering, such as computer-aided sorting and analysis of measurement data, and the recognition and explanation of correlations.

A common knowledge representation and data access allows the scientific exploitation of existing data sources with data-based methods (such as image recognition, measurement uncertainty calculations, factor analysis or material characterization) and simplifies bidirectional knowledge and data transfer between engineers and NDT specialists.

How to cite: Moreno-Torres, B., Völker, C., and Kruschwitz, S.: An Ontology-based approach to enable data-driven research in the field of NDT in Civil Engineering, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12125, https://doi.org/10.5194/egusphere-egu21-12125, 2021.

EGU21-8798 | vPICO presentations | GI2.1 | Highlight

Uncertainty quantification for a sparse machine learning (ML) data set in non-destructive testing in civil engineering (NDT-CE) 

Christoph Völker, Sabine Kruschwitz, and Philipp Benner

ML has been successfully applied to solve many NDT-CE tasks. This is usually demonstrated with performance metrics that evaluate the model as a whole based on a given set of data. However, since in most cases the creation of reference data is extremely expensive, the data used is generally much sparser than in other areas, such as e-commerce. As a result, performance indicators often do not reflect the practical applicability of the ML model. Estimates that quantify transferability from one case to another are necessary to meet this challenge and pave the way for real world applications.

In this contribution we invetigate the uncertainty of ML in new NDT-CE scenarios. For this purpose, we have extended an existing training data set for the classification of corrosion damage by a new case study. Our data set includes half-cell potential mapping and ground-penetrating radar measurements. The measurements were performed on large-area concrete samples with built-in chloride-induced corrosion of reinforcement. The experiment simulated the entire life cycle of chloride induced exposed concrete components in the laboratory. The unique ability to monitor deterioration and initiate targeted corrosion initiation allowed the data to be labelled - which is crucial to ML. To investigate transferability, we extend our data by including new design features of the test specimen and environmental conditions. This allows to express the change of these features in new scenarios as uncertainties using statistical methods. We compare different sampling and statistical distribution-based approaches and show how these methods can be used to close knowledge gaps of ML models in NDT.

How to cite: Völker, C., Kruschwitz, S., and Benner, P.: Uncertainty quantification for a sparse machine learning (ML) data set in non-destructive testing in civil engineering (NDT-CE) , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8798, https://doi.org/10.5194/egusphere-egu21-8798, 2021.

EGU21-8293 | vPICO presentations | GI2.1

BIM and GIS integration for infrastructure analysis

Alessandro Di Benedetto, Salvatore Barba, Margherita Fiani, Marco Limongiello, and Anna Sanseverino

The use of Building Information Modeling (BIM) is certainly increasing, especially in the field of Civil Engineering and Architecture. In recent years, research for new solutions has focused on the integration of BIM and GIS (Geographic Information System), referred to as GeoBIM. Most applications focus on issues related to the import and interoperability of BIM data into a GIS environment and vice versa. Data integration in a well-designed GeoBIM should address the following aspects: i) data harmonization and consistency (e.g., accuracy estimation, geometric and semantic representation, amount of detail, geo-referencing); ii) interoperability of data coming from different sources; iii) transformation of a set of data into a standardized format. One of the most evident inconsistencies if working with BIM or GIS is in the georeferencing of data: BIM designers work in a local Cartesian system while the terrain morphology is referred to a Geodetic Reference System, in the case of Europe, and therefore also for Italy, such system is the ETRS89, realization ETRF2000. The objective of this work is to achieve a true integration between BIM and GIS through the use and combination of the strengths of both technologies: the semantic and spatial component of GIS with the 3D and detailed information coming from the BIM model. A model that meets these requirements will allow a management of the structure and / or infrastructure in a wider and more complete context; therefore, not only at the local level but will be applicable to structures that have a strong impact with the territory and located in areas subject to hydrogeological risk. One of the innovative aspects of the study is the integration of the regional Topographic Database (TDB) with the altimetric component extracted automatically from LiDAR data; the process aims to allow the reconstruction of the volumes in an automated way of each object to define the 3D spatial attribute for the purposes of three-dimensional modeling. The study area is located near the “Monti Lattari” in the Campania Region, in southern Italy. The whole area consists of areas exposed to high hydrogeological risk, characterized by the presence of a complex infrastructural network (railway, highway, national and provincial roads), rich in viaducts, tunnels and galleries. In details, the GeoBIM model of a viaduct (Olivieri Viaduct), built between the years ‘50 and ‘60, has been made. The main structure is a Maillart-arch-type bridge, made of reinforced concrete with a continuous frame deck and two access viaducts. The structural model has been generated from the point cloud acquired by Terrestrial Laser Scanner (TLS). The BIM model has been realized by using Revit software package (Autodesk), which allowed to organize the information useful to define the entire viaduct: each virtual element has been “informed” with all the parameters and characteristics of the structural elements. The next work phase was addressed to the design of a workflow able to combine the BIM model into a GIS developed by using ESRI tools. So, the parametric model produced in Revit is transformed into a GeoDatabase.

How to cite: Di Benedetto, A., Barba, S., Fiani, M., Limongiello, M., and Sanseverino, A.: BIM and GIS integration for infrastructure analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8293, https://doi.org/10.5194/egusphere-egu21-8293, 2021.

EGU21-15804 | vPICO presentations | GI2.1

An Ontology-based Visual Analytics for Apple Variety Testing

Ekaterina Chuprikova, Abraham Mejia Aguilar, and Roberto Monsorno

Increasing agricultural production challenges, such as climate change, environmental concerns, energy demands, and growing expectations from consumers triggered the necessity for innovation using data-driven approaches such as visual analytics. Although the visual analytics concept was introduced more than a decade ago, the latest developments in the data mining capacities made it possible to fully exploit the potential of this approach and gain insights into high complexity datasets (multi-source, multi-scale, and different stages). The current study focuses on developing prototypical visual analytics for an apple variety testing program in South Tyrol, Italy. Thus, the work aims (1) to establish a visual analytics interface enabled to integrate and harmonize information about apple variety testing and its interaction with climate by designing a semantic model; and (2) to create a single visual analytics user interface that can turn the data into knowledge for domain experts. 

This study extends the visual analytics approach with a structural way of data organization (ontologies), data mining, and visualization techniques to retrieve knowledge from an extensive collection of apple variety testing program and environmental data. The prototype stands on three main components: ontology, data analysis, and data visualization. Ontologies provide a representation of expert knowledge and create standard concepts for data integration, opening the possibility to share the knowledge using a unified terminology and allowing for inference. Building upon relevant semantic models (e.g., agri-food experiment ontology, plant trait ontology, GeoSPARQL), we propose to extend them based on the apple variety testing and climate data. Data integration and harmonization through developing an ontology-based model provides a framework for integrating relevant concepts and relationships between them, data sources from different repositories, and defining a precise specification for the knowledge retrieval. Besides, as the variety testing is performed on different locations, the geospatial component can enrich the analysis with spatial properties. Furthermore, the visual narratives designed within this study will give a better-integrated view of data entities' relations and the meaningful patterns and clustering based on semantic concepts.

Therefore, the proposed approach is designed to improve decision-making about variety management through an interactive visual analytics system that can answer "what" and "why" about fruit-growing activities. Thus, the prototype has the potential to go beyond the traditional ways of organizing data by creating an advanced information system enabled to manage heterogeneous data sources and to provide a framework for more collaborative scientific data analysis. This study unites various interdisciplinary aspects and, in particular: Big Data analytics in the agricultural sector and visual methods; thus, the findings will contribute to the EU priority program in digital transformation in the European agricultural sector.

This project has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 894215.

How to cite: Chuprikova, E., Mejia Aguilar, A., and Monsorno, R.: An Ontology-based Visual Analytics for Apple Variety Testing, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15804, https://doi.org/10.5194/egusphere-egu21-15804, 2021.

EGU21-4508 | vPICO presentations | GI2.1

Geophysical characterization of an engineering infrastructure: laboratory tests.

Giacomo Fornasari, Luigi Capozzoli, Gregory De Martino, Valeria Giampaolo, and Enzo Rizzo

The increase of the metropolises stresses the urban areas and intensive planning works is necessary. Therefore, the development of new technologies and methodologies able to explore the subsoil and manage its resources in urban areas becomes an important source in terms of saving time and money. In the last decade, a new subdiscipline in the Applied Geophysics started: Urban Geophysics (Lapenna, 2017). Urban Geophysics analyzes the contribute, in terms of limits and potentialities, that geophysical methodologies can give for providing useful information about the subsoil, environment, buildings and civil infrastructures and supporting the public administrations in planning interventions in urban scenarios.

This work introduces a laboratory test, that was performed at the Hydrogeosite CNR-IMAA laboratory of Marsico Nuovo (Basilicata region, Italy). The test consisted in a multisensor geophysical application on an analogue engineering model. Thanks to the possibility to work in laboratory conditions, a detailed knowledge of the structure was available, providing great advantages for assess the capability of the geophysical methodologies for analyze engineering issues, regarding the characterization of the infrastructural critical zone placed at the interface soil-structure. For this purpose, geoelectrical and electromagnetic methodologies, including Cross hole Electrical Resistivity Tomography and Ground Penetrating Radar, were used to characterize the geometry of the foundation structures and the disposition of the rebar for the reinforced concrete frame. Finally, new geophysical approaches were applied in order to define the corrosion rate of reinforcement.

How to cite: Fornasari, G., Capozzoli, L., De Martino, G., Giampaolo, V., and Rizzo, E.: Geophysical characterization of an engineering infrastructure: laboratory tests., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4508, https://doi.org/10.5194/egusphere-egu21-4508, 2021.

EGU21-13191 | vPICO presentations | GI2.1 | Highlight

Multi-sensing geophysical surveys at the Archaeological Park of Paestum: the discovery of a small Doric temple

Ilaria Catapano, Luigi Capozzoli, Giovanni Ludeno, Gianluca Gennarelli, Gregory De Martino, Enzo Rizzo, Francesco Uliano Scelza, Gabriel Zuchtriegel, and Francesco Soldovieri

Nowadays, non-invasive sensing technologies working at different spatial scales represent a recognized tool to support archaeological researches, because their deployment and cooperative use allow detection and localization of buried ruins before performing excavation. Therefore, they get significant advantages in planning the stratigraphic assays, while reducing costs and times, and support holistic approaches where cultural heritage management, protection and fruition aspects are considered under a unified context.

As a further example among those available in literature, this communication summarizes a successful case study carried out at the Archaeological site of Paestum, sited in the southern Italy [1].

Based on the analysis of aerial imagery and several unexpected archaeological findings, terrestrial measurement campaigns, involving magnetometer (MGA) [2] and ground penetrating radar (GPR) [3] methodologies, were carried out in the northwest quarter of the ancient city near the fortification wall and few meters away from the gate of Porta Marina. As detailed in [4], the MGA was exploited to investigate a large subsurface area in a relatively short time and allowed the identification of the most significant archaeological anomalies, by accounting for the variations of the earth magnetic field due to the different magnetic susceptibilities of construction materials and the magnetic characteristics of the shallow subsoil. The georeferenced MGA image was exploited to select the area requiring a further and more detailed survey, which was performed by means of GPR. Then, GPR data were processed by means of a microwave tomography based approach [4], which allowed a high resolution three dimensional reconstruction of buried targets starting from the electromagnetic field that they backscatter when illuminated by a known incident field. By doing so, detailed information about depth, shape, and orientation of the buried targets were retrieved and an impressive visualization of the the basement of the structure was achieved.

The area is currently under excavation and the initial discovered ruins fully confirm the hypotheses formulated on the basis of the elements found on the surface, the photo interpretations and geophysical investigations. The proposed reconstructive hypothesis of the building as a whole is a stylobate of 10.83 m x 6.80 on which 4 x 7 columns were arranged, with a significantly increased intercolumniation on the short sides (2.02 m) compared to the long sides (1.68 m).

[1] https://www.museopaestum.beniculturali.it/?lang=en

[2] A. Aspinall, C. Gaffney, A. Schmidt, A Magnetometry for archaeologists. Geophysical methods for archaeology, Altamira Press, Lanham, (2008).

[3] D. J. Daniels, Ground penetrating radar, IET, (2004).

[4] Capozzoli, L.; Catapano, I.; De Martino, G.; Gennarelli, G.; Ludeno, G.; Rizzo, E.; Soldovieri, F.; Uliano Scelza, F.; Zuchtriegel, G. The Discovery of a Buried Temple in Paestum: The Advantages of the Geophysical Multi-Sensor Application. Remote Sens. 2020, 12, 2711.

How to cite: Catapano, I., Capozzoli, L., Ludeno, G., Gennarelli, G., De Martino, G., Rizzo, E., Scelza, F. U., Zuchtriegel, G., and Soldovieri, F.: Multi-sensing geophysical surveys at the Archaeological Park of Paestum: the discovery of a small Doric temple, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13191, https://doi.org/10.5194/egusphere-egu21-13191, 2021.

EGU21-16316 | vPICO presentations | GI2.1 | Highlight

Retrieving signs of buried historical roads by GPR: preliminary results from Villa dei Sette Bassi in Rome

Luca Bianchini Ciampoli, Andrea Benedetto, Alessandra Ten, Carla Maria Amici, and Roberta Santarelli

Ground Penetrating Radar has widely proven to be an effective tool for archaeological purposes [1, 2]. Our contribution concerns a geophysical experimental activity carried out in the Complex of Villa dei Sette Bassi, an archaeological site located in Rome, Italy.

In particular, the area was hypothesized to be interested by the track of the ancient via Latina [3, 4], which was the main internal route that connected Rome with the ancient Region of Campania; it ran parallel to the Via Appia, but it was built way before it.

The historical evolution of this landscape has seen great changes since the Middle Ages with a new economy that designed new parcels, new land uses and the stripping of building material from ancient remains: activities that have profoundly altered the territory in its appearance and functioning but also its road network. The uncontrolled building development, has over time hidden the ancient road network, today witnessed only by decontextualized monuments immersed in modern urbanization. Accordingly, great portion of the ancient via Latina remains still buried.

This works reports on the outcomes of the geophysical tests conducted within the area of Villa dei Sette Bassi, with the specific goal of locating the buried track of the via Latina. The survey has been carried out by using multi-frequency ground penetrating radar (GPR) systems with different central frequencies. In detail, a preliminary low frequency analysis was conducted over the entire area that was indicated to be interested by the hidden remains by literary sources, to the intent of detecting the position of the buried road with higher accuracy. Based on the this, a second survey with higher resolution was conducted over a regularly spaced grid.

As a result, GPR tests have returned a coherent reflection pattern that is reasonably representative of a road subgrade/embankment. According to the preliminary archaeological interpretations, these results are most likely related to the historical track of via Latina, even though inspection pits are required in order to verify these assumptions.

In conclusion, GPR demonstrated a great applicability to archaeological purposes, i.e. to detect buried remains and to interpret the function of buried structures, despite the reliability and productivity of the data interpretation are strongly influenced by the expertise of both the geophysicists and the archaeologists involved.

 

References

[1] Bianchini Ciampoli, L., Santarelli, R., Loreti, E.M., Ten, A., Benedetto, A. {2020} “Structural detailing of buried Roman baths through GPR inspection”, Archaeological Prospections, In Press.

[2] Milligan, R., & M., Atkin, {1993}. The use of ground-probing radar within a digital environment on archaeological sites, in Andresen, J., Madsen, T. and Scollar, I., eds., Computing the Past: Computer Application and Quantitative methods in Archaeology: Aarhus, Denmark, Aarhus University Press, pp. 285–291.

[3] Monti, P.G. {1995} “Via Latina”, Istituto Poligrafico e Zecca dello Stato. Libreria dello Stato Roma.

[4] Rea, R., Montella, F., Egidi, R.. Alteri, R., Diamanti, F., Mongetta, M., {2005} “Via Latina”, in Lexicon Topographicum Urbis Romae, III, pp. 133-202, Quasar ed., Roma.

How to cite: Bianchini Ciampoli, L., Benedetto, A., Ten, A., Amici, C. M., and Santarelli, R.: Retrieving signs of buried historical roads by GPR: preliminary results from Villa dei Sette Bassi in Rome, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16316, https://doi.org/10.5194/egusphere-egu21-16316, 2021.

EGU21-16517 | vPICO presentations | GI2.1

A Revised Complex Refractive Index Model for Inferring the Permittivity of Heterogeneous Concrete Models

Hossain Zadhoush, Antonios Giannopoulos, and Iraklis Giannakis

The estimation of the bulk permittivity of heterogeneous mixtures is of great interest for many Ground Penetrating Radar (GPR) and electromagnetic sensing applications [1], [2]. The most used method for estimating the bulk permittivity is the Complex Refractive Index Model (CRIM). The simplicity of this method is one its advantages however, the accuracy of the permittivity estimation has not been tested. Here, the CRIM model’s shape factor is examined and optimised in order to achieve a more accurate concrete bulk permittivity estimation. The concrete components are aggregate particles, cement particles, air-voids and moisture content; and they are randomly distributed with different volume percentages to produce various combinations. These combinations are modelled using the Finite-Difference Time-Domain (FDTD) method as it is an accurate and computationally efficient method [3]. The numerical modelling is then used to predict the bulk permittivity allowing to fine-tune CRIM model’s shape factor. The models are modelled in 3D and a GSSI-like antenna structure is used as the transmitting source [4]. The permittivity estimation uses an accurate time-zero method, which increases the accuracy of the estimated bulk permittivity hence, the shape factor [5], [6]. The results have shown that the optimised CRIM model over-performs the original CRIM model shape factor therefore, a better and more accurate bulk permittivity estimation is achieved for concrete mixtures.

 

References

[1] Daniels, D. J., (2004), Ground Penetrating Radar, 2nd ed. London, U.K., Institution of Engineering and Technology.

[2] Annan, A. P., (2005), Ground Penetrating Radar,  in Investigations in Geophysics, Society of Exploration Geophysicists, pp. 357-438.

[3] Taflove, A., Hagness, S. C., (2005), Computational electromagnetic: The Finite-Difference Time-Domain Method, Artech House, Norwood.

[4] Warren, C., & Giannopoulos, A., (2011), Creating Finite-Difference Time-Domain Models of Commercial Ground Penetrating Radar Antenna Using Taguchi’s Optimization Method, Geophysics, 76(2), G37-G47.

[5] Zadhoush, H., Giannopoulos, A., Giannakis, I., (2020), Optimising GPR time-zero adjustment and two-way travel time wavelet measurement using a realistic 3D numerical model, Near Surface Geophysics, Under review (Minor revisions).

[6] Zadhoush, H., (2020), Numerical Modelling of Ground Penetrating Radar for Optimization of the Time-zero Adjustment and Complex Refractive Index Model, PhD Thesis Submitted at The University of Edinburgh.

How to cite: Zadhoush, H., Giannopoulos, A., and Giannakis, I.: A Revised Complex Refractive Index Model for Inferring the Permittivity of Heterogeneous Concrete Models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16517, https://doi.org/10.5194/egusphere-egu21-16517, 2021.

EGU21-8845 | vPICO presentations | GI2.1

A GPR based estimation of concrete strength changes under extreme temperatures exposure: An experimental study

Salih Serkan Artagan, Özgür Yurdakul, Vladislav Borecky, and Miroslav Lunak

There are certain situations where concrete structures are required to resist high temperatures. This applies to cases where exposure to high temperature is expected due to the special character of buildings or where the concrete structure is required to resist severe conditions caused by traffic accidents, terrorist attacks, or natural disasters (earthquakes, fires, etc.). Under such applications, the effect of elevated temperature on mechanical and physical properties may determine whether the concrete element or structure will maintain its structural integrity or not. In this context, fire resistance is defined as the ability to withstand exposure to fire without loss of load-bearing function or ability to act as a barrier to spread a fire. In most cases, structural health monitoring of concrete structures is performed as the visual appraisal of the external characteristics of structures or destructive testing (e.g., concrete coring), and little use has been made of the modern non-destructive testing (NDT) techniques including Ground Penetrating Radar (GPR). GPR, emitting short pulses of electromagnetic energy into the material, is primarily used for location of rebar, estimation of rebar size, industrial quality control, defect and decay detection, and measurement of electrical properties, in case of concrete diagnostics.

This paper comprises a series of GPR and core compressive strengths on low-strength concrete samples. The samples were produced and tested by GPR before and after extreme temperature exposure in an electric furnace at the following temperature levels: 300, 400, 500, 600, and 700 ℃. Then, the compressive test results of the cores taken from the specimens are compared with the GPR data for each temperature level. For GPR tests, the IDS Aladdin system was used with a double polarized 2 GHz antenna. For compressive strength tests, a compression test machine with a capacity of 3000 kN was used.

Based on GPR measurement, Relative Dielectric Permittivity (RDP) values were calculated based on known dimensions of samples and two-way travel time (twt) values obtained from A-scans. The change in RDP values of samples before and after exposure to extreme temperature was then calculated. This variation was then correlated with the change of compressive strength values with regard to the applied temperature levels. This experimental study thus gives an insight into the potential use of GPR, as an NDT tool, in estimating the strength loss in concrete structural elements exposed to aggressive fire.

All GPR tests were conducted in Educational and Research Centre in Transport; Faculty of Transport Engineering; University of Pardubice. This work is supported by the University of Pardubice (Project No: CZ.02.2.69/0.0/0.0/18_053/0016969).

How to cite: Artagan, S. S., Yurdakul, Ö., Borecky, V., and Lunak, M.: A GPR based estimation of concrete strength changes under extreme temperatures exposure: An experimental study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8845, https://doi.org/10.5194/egusphere-egu21-8845, 2021.

Ground Penetrating Radar was used in this study as a non-destructive geophysical method. The main objective of this research is focused on enhancing the local seismic soil site analysis. The study employs GPR images to determine changes in the ground that can be associated with changes on the seismic soil response. To determine the GPR capacity in detecting changes in the ground materials and improve new methodologies of the radar data processing.

Results could be used to improve the selection of areas for more intensive scrutiny, enhancing the analysis of local seismic behaviour studies. Soil site studies are crucial in the analysis of seismic hazard in populated areas. This study and analysis will be carried out in an urban environment at the Sant Pau Hospital in Barcelona city (Spain). Data were acquired in the field along with two different directions: parallel and perpendicular to the coastline of the Mediterranean Sea in Barcelona city.

The procedure is based in integrated data from the laboratory experiments by using 1600 MHz centre frequency and obtaining real GPR field images in the field by using 25 MHz centre frequency antenna in the Sant Pau Hospital. Therefore, radar data will be first processed using the commercial software ReflexW, followed by a more specific processing sequence (both in amplitude and frequency domains) with a specific algorithm developed with MATLAB.

Finally, the mathematical processing of the radargrams in terms of water content compared to the information based on historical maps. Results show that GPR is a promising method and compared to previous studies a good agreement was observed in this specific case study. 

How to cite: Rasol, M., Perez-Gracia, V., and Santos, S.: New methodologies of GPR Assessment for analysing water content in sedimentary deposits; Application to the Hospital Sant Pau Urban Area in Barcelona, Spain, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-363, https://doi.org/10.5194/egusphere-egu21-363, 2021.

Signal polarity is an attribute that can be used as additional key element to reduce ambiguities and pitfalls in the data interpretation step.

A theoretical analysis of the reflection and transmission phenomena for parallel and perpendicular polarization of the electric field was carried out highlighting that polarity changes (180-degree phase shifts) are caused only by reflection phenomena in specific conditions.

Numerical modelling, through the Finite Difference Time Domain (FDTD) method, helped visualize the theoretical findings and was employed to reproduce the GPR response in two simple contexts (high permittivity layer embedded in a lower permittivity material and vice versa). The findings showed the expected theoretical polarity of multiple reflections providing a tool to effectively recognise them along with travel time information and reflection shapes.

The FDTD technique was also used to analyse the polarity response of regular geometrical shaped air-filled cavities (circle, square and arched roof square), in lossless and lossy conditions. The output was then compared with real radargrams concluding that A-scan assessment should be considered when pronounced scattering and attenuation phenomena are experienced (although polarity analysis may not be possible in very complex environments) and that the shape of the target may affect the resulting signal polarity due to interference with other wave fields.

Polarity analysis should be carried out by comparing the direct wavelet with the signal pattern of interest to assess if a phase shift occurred: attention should be paid to the GPR system used as not all the GPR antennas record the direct wavelet.

How to cite: Campo, D.: On GPR signal polarity: a comparison between theoretical findings and real case-studies, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9234, https://doi.org/10.5194/egusphere-egu21-9234, 2021.

EGU21-11199 | vPICO presentations | GI2.1

Intelligent recognition of underground pipeline From GPR image based on Hash algorithm

Bo Li and Yonghui Zhao

Ground penetrating radar (GPR) is a high-resolution geophysical non-destructive detection method, which is widely used in near surface target detection, and has been successfully applied in urban construction and geotechnical engineering. In urban life, underground pipelines undertake important missions such as energy transmission and information transmission. As the basic data of smart city, the acquisition of spatial location information of underground pipelines depends on geophysical detection data such as GPR. The traditional recognition and interpretation of  GPR underground pipeline image mainly depends on and is seriously limited by the professional experience of the staff, which is very disadvantageous to the development of large-scale urban underground pipeline survey. To address this problem, according to the GPR reflection image characteristics of isolated targets such as underground pipelines, this paper proposes an intelligent recognition concept of isolated targets in GPR profile based on CBIR (Content-based image retrieval) According to Hash algorithm and improved vector K-means clustering analysis, the intelligent detection, automatic image sorting and recognition of underground pipeline target in GPR profile are realized. Finally, the pipeline material is judged by extracting the image brightness function of the middle trace in the recognition area. The application results of numerical simulation experiments and measured data show that this algorithm can effectively identify the hyperbolic characteristics of the pipeline in the GPR profile, and the identified area can accurately reflect the spatial location of the underground pipeline.

How to cite: Li, B. and Zhao, Y.: Intelligent recognition of underground pipeline From GPR image based on Hash algorithm, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11199, https://doi.org/10.5194/egusphere-egu21-11199, 2021.

EGU21-12852 | vPICO presentations | GI2.1

Combined Migration of GPR data for layered media

Raffaele Persico and Gianfranco Morelli

In this contribution we will propose the combination of migration results achieved from the same GPR dataset, aimed to mitigate the effects of the nonuniformity of the propagation velocity of the waves throughout the investigated domain. The nonuniformity of the propagation velocity can be appreciated from the diffraction hyperbolas [1] possibly present in the data, or directly from the results of the focusing [2] achieved from different trial values of the propagation velocity. In ref. [3] an algebraic combination of two (but theoretically even more) migration results achieved from different migration parameters applied to the same data has been shown. In that paper, the case of a horizontal variation and the case of a vertical variation of the propagation velocity of the electromagnetic waves in the soil were considered. Here, we will consider the case of a layered medium with non-flat interface between two adjacent layers, which is a case of interest in several practical application, and is a case where we have both a vertical and a horizontal variation of the parameters. Analogously to ref. [3], we will consider both the aspect of the focusing and that of the combined time-depth conversion.

 

References

 

[1] R. Persico G. Leucci, L. Matera, L. De Giorgi, F. Soldovieri, A. Cataldo, G. Cannazza, E. De Benedetto, Effect of the height of the observation line on the diffraction curve in GPR prospecting, Near Surface Geophysics, Vol. 13, n. 3, pp. 243-252, 2015.

[2]G. Gennarelli, I. Catapano, F. Soldovieri, R. Persico, On the Achievable Imaging Performance in Full 3-D Linear Inverse Scattering, IEEE Trans. on Antennas and Propagation,  vol. 63, n. 3, pp. 1150-1155, March 2015.

[3] R. Persico, G. Morelli, Combined Migrations and Time-Depth Conversions in GPR Prospecting: Application to Reinforced Concrete, Remote Sens. 2020, Volume 12, Issue 17, 2778, open access, DOI 10.3390/rs12172778

 


 

How to cite: Persico, R. and Morelli, G.: Combined Migration of GPR data for layered media, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12852, https://doi.org/10.5194/egusphere-egu21-12852, 2021.

EGU21-14803 | vPICO presentations | GI2.1

Joint petrophysical full-waveform inversion of the shallow-seismic and multi-offset GPR data

Tan Qin, Thomas Bohlen, and Yudi Pan

Shallow-seismic surface wave and ground penetrating radar (GPR) are employed in a wide range of engineering and geosciences applications. Full-waveform inversion (FWI) of either seismic or multi-offset GPR data are able to provide high-resolution subsurface characterization and have received particular attention in the past decade. Those two geophysical methods are involved in the increasing requirements of comprehensive site and material investigations. However, it is still challenging to provide an effective integration between seismic data and electromagnetic data. In this paper, we investigated the joint petrophysical inversion (JPI) of shallow-seismic and multi-offset GPR data for more consistent imaging of near surface. As a bridge between the seismic parameters (P-wave velocity, S-wave velocity, and density) and GPR parameters (relative dielectric permittivity and electric conductivity), the petrophysical relationships with the parameters namely porosity and saturation are employed to link two data sets. We first did a sensitivity analysis of the petrophysical parameters to the seismic and GPR parameters and then determined an efficient integration of using shallow-seismic FWI to update porosity and GPR FWI to update saturation, respectively. A comparison of several parameterisation combinations shows that the seismic velocity parameterisation in shallow-seismic FWI and a modified logarithm parameterisation in GPR FWI works well in reconstructing reliable S-wave velocity and relative dielectric permittivity models, respectively. With the help from the petrophysical links, we realized JPI by transforming those well recovered parameters to the petrophysical parameters and then to other seismic and GPR parameters. A synthetic test indicates that, compared with the individual petrophysical inversion and individual FWI, JPI outperforms in simultaneously reconstructing all seismic, GPR, and petrophysical parameters with higher resolution and improved details. It is proved that JPI would be a potential data integration approach for the shallow subsurface investigation.

How to cite: Qin, T., Bohlen, T., and Pan, Y.: Joint petrophysical full-waveform inversion of the shallow-seismic and multi-offset GPR data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14803, https://doi.org/10.5194/egusphere-egu21-14803, 2021.

EGU21-13463 | vPICO presentations | GI2.1 | Highlight

On the Use of Short-Time Fourier Transform for the Analysis of Tree Root Systems using Ground Penetrating Radar

Livia Lantini, Fabio Tosti, Luca Bianchini Ciampoli, and Amir M. Alani

Monitoring and protecting natural assets is increasingly important today, as aggressive pathogens are negatively impacting the trees' survival. In this regard, root systems are affected by fungal infections that cause roots’ rot and eventually lead to trees' death. Such disease can spread rapidly to the adjacent trees and affect larger areas. Since these decays generally do not display visible signs, early identification is the key to tree preservation.

Within this context, non-destructive testing (NDT) methods are becoming popular, being more versatile than destructive methods. Specifically, ground penetrating radar (GPR) is emerging as an accurate geophysical method for tree root mapping. Recent research has focused on implementing automated algorithms for 3D root mapping, improving root detection through advanced GPR signal processing and the estimation of tree roots' mass density [1]. Also, recent studies have proven that GPR is effective in mapping the root system's architecture of street trees [2].

The present research reports the preliminary results of an experimental study, conducted to investigate the feasibility of a novel tree root assessment methodology based on the analysis of GPR data both in time and frequency domain. To this end, data were processed using a short-time Fourier transform (STFT) approach [3], which allows the evaluation of how the frequency spectrum changes across the signal propagation time window. The suggested processing system may be implemented for expeditious analyses or on trees challenging to access, such as in urban environments, where more comprehensive survey methods are not applicable. The objectives of this study, therefore, are to investigate how different features (i.e., roots, layers) affect the time-frequency analysis of GPR data, and to identify recurring patterns in the results to set a coherent data processing methodology.

Results' interpretation has shown the viability of the presented approach in recognising the influence of different features on the analysis of GPR data as it changes over time. This also allowed the detection of recurring patterns in the analysed data, proving that this method is worthy of further investigations.

Acknowledgements
The authors would like to express their sincere thanks and gratitude to the following trusts, charities, organisations and individuals for their generosity in supporting this project: Lord Faringdon Charitable Trust, The Schroder Foundation, Cazenove Charitable Trust, Ernest Cook Trust, Sir Henry Keswick, Ian Bond, P. F. Charitable Trust, Prospect Investment Management Limited, The Adrian Swire Charitable Trust, The John Swire 1989 Charitable Trust, The Sackler Trust, The Tanlaw Foundation, and The Wyfold Charitable Trust.


References
[1]     Lantini, L., Tosti, F., Giannakis, I., Zou, L., Benedetto, A. and Alani, A. M., 2020. "An Enhanced Data Processing Framework for Mapping Tree Root Systems Using Ground Penetrating Radar," Remote Sensing 12(20), 3417.
[2]     Lantini, L., Alani, A., Giannakis, I., Benedetto, A. and Tosti, F., 2020. "Application of ground penetrating radar for mapping tree root system architecture and mass density of street trees," Advances in Transportation Studies (3), 51-62.
[3]     Bianchini Ciampoli, L., Calvi, A. and D'Amico, F., 2019. "Railway Ballast Monitoring by GPR: A Test Site Investigation," Remote Sensing 11(20), 238

How to cite: Lantini, L., Tosti, F., Bianchini Ciampoli, L., and Alani, A. M.: On the Use of Short-Time Fourier Transform for the Analysis of Tree Root Systems using Ground Penetrating Radar, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13463, https://doi.org/10.5194/egusphere-egu21-13463, 2021.

EGU21-14834 | vPICO presentations | GI2.1

A rapid total nitrogen determination prototype for wastewater treatment plants online detection

Jingxuan Geng, Chunhua Yang, Lijuan Lan, Jie Han, Fengxue Zhang, and Yonggang Li

The online automatic detection for the concentration of total nitrogen (TN) is a critical problem in wastewater treatment plants (WWTPs). The over-discharge of TN can cause severe environmental problems such as aquatic eutrophication and ecosystem dysfunction, and the TN concentration in each wastewater treatment process can also reflect the processing statement of WWTPs and ensure its stable operation. However, determining the TN concentration timely is always a difficult task. According to the traditional TN detection approach, the concentration of TN is determined after the oxidative digestion process, which is a complex chemical reaction process and usually requires 30 minutes to 1 hour. Considering the actual operation situation, this traditional method can hardly satisfy the real-time requirement of WWTPs, which can only be used as a kind of validation approach. To solve this problem, in this paper, we design a novel automatic detection prototype of TN. Instead of determining the concentration of TN after the process of oxidative digestion, the ultraviolet spectrum is used to non-destructive detect the concentration of nitrate during the whole oxidative digestion process. Based on the principle of competitive response and chemical reaction kinetics, for different water samples with different TN concentrations, their oxidative digestion processes are different even in the early reaction stage. Therefore, we can use the early reaction properties to determine the TN concentration, thereby shortening the necessary detection time. Based on experimental data collected from real water samples, our prototype can not only efficiently shorten the detection time of the TN concentration, but also ensure satisfactory detection accuracy.

How to cite: Geng, J., Yang, C., Lan, L., Han, J., Zhang, F., and Li, Y.: A rapid total nitrogen determination prototype for wastewater treatment plants online detection, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14834, https://doi.org/10.5194/egusphere-egu21-14834, 2021.

EGU21-7437 | vPICO presentations | GI2.1

Classification of moisture damage in layered building floors with GPR and neutron probe

Tim Klewe, Christoph Strangfeld, Tobias Ritzer, and Sabine Kruschwitz

In 2019, 3.1 billion Euro of damage was caused by piped water, accounting for the largest share (53%) of building insurance claims in Germany. In the event of damage, the accurate determination and localization of water ingress is essential to plan for and perform efficient renovations. Neutron probes are already applied successfully on building floors to localize the source of damage and other affected areas. However, additional information about the depth of moisture penetration can only be obtained by the destructive extraction of drilling cores, which is a time- and cost-intensive procedure. With its high sensitivity to water and fast measurement procedure, Ground Penetrating Radar (GPR) can serve as a suitable extension to the neutron probe, enabling more precise characterization of common forms of moisture damage.

In this research project, we study the influence of common types of moisture damage in differing floor constructions using GPR and a neutron probe. A measurement setup with interchangeable layers is used to vary the screed material (cement or anhydrite) and insulation material (Styrofoam, Styrodur, glass wool, perlite), as well as the respective layer thickness. Every configuration is measured for the following main cases: 1) dry state; 2) with a damaged insulation layer and 3) a damaged screed layer.

The evaluation is focused on the extraction of distinctive signal features for GPR, which can be used to classify the underlying case of damage. Furthermore, possible combinations of these features are investigated using multivariate data analysis and machine learning in order to evaluate the influence of different floor constructions.

To validate the developed methods, practical measurements on real damage cases in Germany are carried out and compared to reference data obtained from drilling cores.

How to cite: Klewe, T., Strangfeld, C., Ritzer, T., and Kruschwitz, S.: Classification of moisture damage in layered building floors with GPR and neutron probe, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7437, https://doi.org/10.5194/egusphere-egu21-7437, 2021.

EGU21-13472 | vPICO presentations | GI2.1

Determining Bridge Deck Chloride Quantities Using Ground Penetrating Radar

Anthony Alongi

Chlorides from deicing salts attack the steel reinforcement in bridge decks which can ultimately cause delamination and deterioration of the concrete. For transportation agencies, the repair cost from these defects are estimated to exceed $5B per year in USA and make up between 50% - 85% of bridge maintenance budgets. While, the removal and replacement of chloride contaminated concrete is the most long-lasting and cost-effective remediation, few methods exist to determine chloride content in bridge decks. This research describes an entirely new method for determining chloride quantity in bridge decks using ground penetrating radar (GPR) technology and establishes and quantifies the relationship between chlorides in concrete (which cause corrosion of reinforcing steel and delamination of concrete) and the effect on GPR signal propagation. Specifically, it shows that there is a deterministic relationship between radar signal attenuation and the amount of chloride and moisture in bridge deck concrete, and that when moisture content is known it is possible to estimate chloride quantity based on signal loss or attenuation measurements. Our research also demonstrates the practical application of this concept by utilizing GPR along with limited coring (three or more core samples) and laboratory chloride measurements to produce an accurate and quantitative, spatial mapping of chlorides in bridge decks.

How to cite: Alongi, A.: Determining Bridge Deck Chloride Quantities Using Ground Penetrating Radar, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13472, https://doi.org/10.5194/egusphere-egu21-13472, 2021.

EGU21-14103 | vPICO presentations | GI2.1

Detection of voids behind segments in the shield tunnels by using Ground Penetrating Radar

Hai Liu, JianYing Lin, Xu Meng, and Yanliang Du

Abstract—Metro traffic in subsurface tunnels is under a rapid development in many cities in the recent decades. However, the voids and other concealed defects inside and/or behind the tunnel lining pose critical threat to the safety of the operating metro tunnels. Ground penetrating radar (GPR) is a non-destructive geophysical technique by transmitting electromagnetic (EM) waves and receiving the reflected signals. GPR has proved its capability in the detection of the existence of tunnel structural defects and anomalies. However, the voids are still hard to be recognized in a GPR image due to the strong scattering clutter caused by the dense steel bars reinforced inside the concrete lining [1]. In this paper, we analyze the propagations of EM waves through reinforce concrete segments of shield tunnels by finite difference time domain (FDTD) simulations and model test.  Firstly, a series of simulations results we have done, indicates that the center frequency of GPR ranges from 400 MHz to 600 MHz has a good penetration through the densely reinforced concrete lining. And the distance between the antennas and the surface of shield tunnel segments should be less than 0.2 m to ensure a good coupling of incident electromagnetic energy into the concrete structure. Then, to image the geometric features of the void behind the segment, reverse-time migration method is applied to the simulated GPR B-scan profile, which presents higher resolution results than the results by using the traditional diffraction stack migration (Figure 1) [2]. Finally, the field experiment results prove that a commercial GPR system operating at a center frequency of 600 MHz do detect a void behind the shield tunnel (Figure 2). The reflection from the void, which starts from the back interface of the segments and lasts over 20 ns, are significantly different from the reflections from the rebars (Figure 3). In summary, GPR has potential in the detection of voids behind the shield tunnel segment. More simulations and field experiments will be performed in the future.

Keywords—ground penetrating radar (GPR); shield tunnel; voids; reverse time migration (RTM)

Acknowledgement—this work was supported by Shenzhen Science and Technology program (grant number:KQTD20180412181337494).

Fig. 1 Numerical simulation of two segments of 2D shield tunnel. (a) numerical model, (b) simulated GPR B-scan profile, (c) migrated profile by using diffraction stack migration and (d) migrated profile by using reverse-time migration.

Fig. 2 One photo of the field experiment.

Fig. 3 GPR reflections from a void behind the segment of a subway tunnel

References

[1]     H. Liu, H. Lu, J. Lin, F. Han, C. Liu, J. Cui, B. F. Spencer, “Penetration Properties of Ground Penetrating Radar Waves through Rebar Grids” , IEEE Geoscience and Remote Sensing Letters ( DOI: 10.1109/LGRS.2020.2995670)

[2]          H. Liu, Z. Long, F. Han, G. Fang, Q. H. Liu, “Frequency-Domain Reverse-Time Migration of Ground Penetrating Radar Based on Layered Medium Green's Functions”, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, vol. 11, no. 08, pp. 2957-2965, 2018.

 

How to cite: Liu, H., Lin, J., Meng, X., and Du, Y.: Detection of voids behind segments in the shield tunnels by using Ground Penetrating Radar, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14103, https://doi.org/10.5194/egusphere-egu21-14103, 2021.

EGU21-14685 | vPICO presentations | GI2.1

Interlayer Debonding Inspection in Airport Pavements by MIMO GPR System

Lilong Zou, Fabio Tosti, Amir M. Alani, and Motoyuki Sato

The integrity and flatness of airport pavement facilities are important to maintain safe operations of aircrafts. Even a small defect and resulting debris can cause catastrophic accidents and, therefore, anomalies must be accurately detected for the first time before major damage occurs. To this effect, it is necessary to develop a low-cost, efficient, and accurate inspection technology to detect the anomalies in airport concrete pavements. In recent years, non-destructive testing (NDT) methods have been widely used in airport pavement inspection and maintenance due to the provision of reliable and efficient information. Amongst the NDT techniques, GPR can provide optimal resolutions for different applications in civil engineering due to the ultra-wide frequency band configuration [1][2]. However, for the investigation of airport pavement facilities main challenges are how to extract information from the reflections by small anomalies [3][4].

In this research, we used a MIMO GPR system to inspect the interlayer debonding in a large area of an airport pavement. A special set of antenna arrangements of the system can obtain common mid-point (CMP) gathers during a common offset survey simultaneously. The existence of interlayer debonding affects the phase of the reflection signals, and the phase disturbance can be quantified by wavelet transform. Therefore, an advanced approach that uses the average entropy of the wavelet transform parameters in a CMP gathers to detect the interlayer debonding in airport pavements is proposed.

The aim of this research is to provide more significant and accurate information for airport pavement inspections using a MIMO GPR system. To this extent, the wavelet entropy analysis is applied to identify the interlayer debonding existed in the shallow region. The proposed approach was then evaluated by field tests on an airport taxiway. The results were validated by on-site coring and demonstrate that the regions with high entropy correspond to the regions where tiny voids occurred. The proposed method has proven potential to detect the interlayer debonding of the pavement model accurately and efficiently.

 

References

[1] Alani, A. M. et al., 2020. Reverse-Time Migration for Evaluating the Internal Structure of Tree-Trunks Using Ground-Penetrating Radar. NDT&E International, vol.115, pp:102294.

[2] Zou, L. et al., 2020. Mapping and Assessment of Tree Roots using Ground Penetrating Radar with Low-Cost GPS. Remote Sensing, vol.12, no.8, pp:1300.

[3] Zou, L. et al., 2020. On the Use of Lateral Wave for the Interlayer Debonding Detecting in an Asphalt Airport Pavement Using a Multistatic GPR System. IEEE Transaction on Geoscience and Remote Sensing, vol. 58, no. 6, pp. 4215-4224.

[4] Zou, L. et al., 2021. Study on Wavelet Entropy for Airport Pavement Debonded Layer Inspection by using a Multi-Static GPR System. Geophysics, in press.

How to cite: Zou, L., Tosti, F., Alani, A. M., and Sato, M.: Interlayer Debonding Inspection in Airport Pavements by MIMO GPR System, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14685, https://doi.org/10.5194/egusphere-egu21-14685, 2021.

EGU21-15100 | vPICO presentations | GI2.1 | Highlight

ERT and GPR surveys for the detection of incipient collapse areas in urban environment

Luigi Capozzoli, Gregory De Martino, Giacomo Fornasari, Valeria Giampaolo, and Enzo Rizzo

Urban Resilience represents the capability of an urban system to preserve its features (in terms of public and private qualities and services) when shock events occur [1]. This topic is receiving an increasing interest for the climate change emergency which require innovative strategies for preserving the natural and anthropic resources present in the subsoil. In this framework, the Urban Geophysics could give a strong contribution to improving the knowledge of the critical issues affecting urban area [2].

One of the most interesting challenges is represented by the detection of ground collapse phenomena that can hardly reduce the safety and reliability of civil structures and infrastructures, as clearly demonstrated by the ground occurred in the Ospedale del Mare car park (Naples, Italy) [3] during the COVID-19 emergency that has brought the light on the weakness of the planning processes of the public authorities when fast decisions are required. Indeed, decision making in urban planning can be effectively supported by rational and reasoned use of the geophysical technologies able to reduce the risks imputable to the activities and decision required by the emergency planning in urban contexts.

This work focuses its attention on the capability of geophysical methodologies to detect, characterize and monitoring the presence of buried sinkholes, collapses, voids within the subsoil able to cause severe structural stability problems with rapid and non-invasive applications based on the use of Ground Penetrating Radar and Electrical Resistivity Tomographies. The studied cases showed how the cooperative use of the geoelectrical and electromagnetic methods can identify and monitor potential risks of collapses highlighting the pros and cons of the two techniques in terms of resolution and depth of study.

 

REFERENCES

[1] Lapenna V. (2016) Resilient and sustainable cities of tomorrow: the role of applied geophysics. Bollettino di Geofisica Teorica ed Applicata 58(4):237–251. https ://doi.org/10.4430/bgta0204

[2] Capozzoli L., De Martino G., Polemio M. et E. Rizzo, Surveys in Geophysics 2019, Geophysicaltechniquesfor monitoring settlement phenomena occurring in reinforced concrete buildings, Surveys in Geophysics, DOI: 10.1007/s10712-019-09554-8;

[3] Borghese L.,  Mortensen A. and R. Picheta, https://edition.cnn.com/2021/01/08/europe/italy-hospital-sinkhole-scli-intl/index.html (latest access 01/20/2021, January 9, 2021

How to cite: Capozzoli, L., De Martino, G., Fornasari, G., Giampaolo, V., and Rizzo, E.: ERT and GPR surveys for the detection of incipient collapse areas in urban environment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15100, https://doi.org/10.5194/egusphere-egu21-15100, 2021.

EGU21-15385 | vPICO presentations | GI2.1

Multi-length TDR probes: future perspectives

Raffaele Persico, Lourdes Farrugia, Iman Farhat, and Charles Sammut

In this contribution we will propose the use of multi-length TDR probes for measurements of the dielectric and possibly magnetic characteristics of a material under test (MUT) as a function of frequency. The multi-length strategy, consisting in making use of a TDR probe with adjustable length of the conductors, can allow the meaningful increase of information achievable about the MUT at each test frequency. We are still at an early stage about these possibilities, and many questions are still open at this time. However, some of our previous studies [1-3] show that the method is promising and can permit the acquisition of some information not intrinsically available from a traditional TDR probe, especially if the MUT shows a dispersive behaviour and possibly magnetic properties. In this contribution, we will discuss the recent work related in particular to geophysical applications.

Acknowledgements

This work in progress is being carried out within the European Cost Action CA17115 Mywave.

References

[1] R. Persico, M. Pieraccini, Measurement of dielectric and magnetic properties of Materials by means of a TDR probe, Near Surface Geophysics, vol. 16, n.2, pp.1-9, DOI:10.3997/1873-0604.2017046, 2018.

[2] R. Persico, I. Farhat, L. Farrugia, S. d’Amico, C. Sammut, An innovative use of TDR probes: First numerical validations with a coaxial cable, Journal of Environmental & Engineering Geophysics, doi.org/10.2113/JEEG23.4.437, 23 (4): 437-442, 2018.

[3] I. Farhat, L. Farrugia, R. Persico, S. D’Amico, and C. Sammut, Preliminary Experimental Measurements of the Dielectric and Magnetic Properties of a Material with a Coaxial TDR Probe in Reflection Mode, Progress In Electromagnetics Research M, Vol. 91, 111–121, 2020.

How to cite: Persico, R., Farrugia, L., Farhat, I., and Sammut, C.: Multi-length TDR probes: future perspectives, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15385, https://doi.org/10.5194/egusphere-egu21-15385, 2021.

EGU21-7920 | vPICO presentations | GI2.1

Nondestructive data analysis for pavement profile evaluation

Christina Plati, Konstantinos Gkyrtis, and Andreas Loizos

Highway pavements serve the need for safe transportation of human being and freights, so their condition deserves continuous monitoring and assessment. However, pavements are most often monitored in terms of their surface performance evaluation. Either with or without surface distresses, excessive pavement unevenness and/or texture loss may lead to a reduced road users’ satisfaction. Most often, the pavement surface condition is sensed through laser profilers that operate at traffic speeds. Once detected through the stand-alone use of laser profilers, pavement roughness along a pavement surface may be of major concern for the related agencies, since the root causes of roughness issues are in most cases unknown.

Excessive unevenness might sometimes be interrelated with structural issues within one or more pavement layers or even issues within the pavement foundation support. Traditionally, coring and boreholes are considered suitable to detect the condition of pavement surface layers and pavement substructure respectively. However, these processes are destructive and time-consuming. On the contrary, Non-Destructive Testing

(NDT) can be alternatively used to rapidly evaluate potential structural problems at areas with roughness issues and identify areas for further investigation. A popular method to assess the pavement structural integrity is the use of nondestructive deflectometric tests, including the Falling Weight Deflectometer (FWD). This kind of testing outperforms the traditional approach; thus it is both desirable and practical.

On these grounds, related research is pursued towards integrating pavement profile and deflectometric data in order to further evaluate indications of increased pavement roughness. In particular, Long Term Pavement Performance (LTPP) data including deflectometric and pavement profile data is used. Additional sensing data through geophysical inspections with the Ground Penetrating Radar (GRP) is used to assist the overall pavement assessment. The study demonstrates the power of pavement sensing data in order to provide the related agencies with cost-effective and reliable evaluation methods and approaches.

How to cite: Plati, C., Gkyrtis, K., and Loizos, A.: Nondestructive data analysis for pavement profile evaluation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7920, https://doi.org/10.5194/egusphere-egu21-7920, 2021.

As an array antenna ground penetrating radar (GPR) system electronically switches any antenna combinations sequentially in milliseconds, multi-offset gather data, such as common mid-point (CMP) data, can be acquired almost seamlessly. However, due to the inflexibility of changing the antenna offset, only a limited number of scans can be obtained. The array GPR system has been used to collect time-lapse GPR data, including CMP data during the field infiltration experiment (Iwasaki et al., 2016). CMP data obtained by the array GPR are, however, too sparse to obtain reliable velocity using a standard velocity analysis, such as semblance analysis. We attempted to interpolate the sparse CMP data based on projection onto convex sets (POCS) algorithm (Yi et al., 2016) coupled with NMO correction to automatically determine optimum EM wave velocity. Our previous numerical study showed that the proposed method allows us to determine the EM wave velocity during the infiltration experiment.

The main objective of this study was to evaluate the performance of the proposed method to interpolate sparse array antenna GPR CMP data collected during the in-situ infiltration experiment at Tottori sand dunes. The interpolated CMP data were then used in the semblance analysis to determine the EM wave velocity, which was further used to compute the infiltration front depth. The estimated infiltration depths agreed well with independently obtained depths. This study demonstrated the possibility of developing an automatic velocity analysis based on POCS interpolation coupled with NMO correction for sparse CMP collected with array antenna GPR.

How to cite: Oikawa, K., Saito, H., Kuroda, S., and Takahashi, K.: Determining optimum wave velocity from sparse CMP automatically by coupling POCS interpolation and NMO correction: application to array antenna GPR data collected during in-situ infiltration test, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9074, https://doi.org/10.5194/egusphere-egu21-9074, 2021.

EGU21-15147 | vPICO presentations | GI2.1

Bridge monitoring and deformation time-series analysis by high-resolution Multi-Temporal SAR Interferometry (MT-InSAR) 

Valerio Gagliardi, Luca Bianchini Ciampoli, Amir Alani, Fabio Tosti, and Andrea Benedetto

Multi-temporal Interferometric Synthetic Aperture Radar (InSAR) is a space-borne monitoring technique capable of detecting cumulative surface displacements with millimeter accuracy in the Line of Sight (LOS) of the radar sensor [1-3]. Several developments in the processing methods and the increasing availability of SAR datasets from different satellite missions, have proven the viability of this technique in the near-real-time assessment of bridges and the health monitoring of transport infrastructures [2-4].

This research aims to demonstrate the potential of satellite-based remote sensing techniques as an innovative health-monitoring method for structural assessment of bridges and the prevention of damages by structural subsidence, using high-resolution SAR datasets integrated with complementary Ground-Based (GB) Non-Destructive Testing (NDT) techniques. To this purpose, high-resolution COSMO‐SkyMed (CSK) products provided by the Italian Space Agency (ASI) were acquired and processed.

In particular, a multi-temporal InSAR analysis was developed to identify and monitor the structural displacements of the Rochester Bridge, located in Rochester, Kent, UK. To this extent, a clustering operation is realised to collect the identified Persistent Scatterers (PSs) over the structural elements of the bridge (i.e., bridge piers and arcs). Furthermore, several sub-clusters with a comparable deformation trend were identified and located over the bridge elements. This operation paves the way for an automatisation of the process through a Machine Learning (ML) clustering algorithms to assign each PS data-point to specific groups, based on the structural element type and the trend of seasonal deformation time-series.

The outcomes of this study demonstrate how multi-temporal InSAR remote sensing techniques can be synergistically applied to complement non-destructive ground-based analyses, paving the way for future integrated methodologies in the monitoring of infrastructure assets.

Acknowledgments: The authors want to acknowledge the Italian Space Agency (ASI) for providing the COSMO-SkyMed Products® (©ASI, 2017-2019),  in the framework of the ASI-Open Call Project “MoTIB, ID 742” accepted by ASI. In addition, the authors would like to acknowledge the Rochester Bridge Trust for facilitating and supporting this research. This research is supported by the Italian Ministry of Education, University and Research under the National Project “EXTRA TN”, PRIN 2017, Prot. 20179BP4SM.

References

[1] Alani A. M., Tosti F., Bianchini Ciampoli L., Gagliardi V., Benedetto A., Integration of GPR and InSAR methods for the health monitoring of masonry arch bridges. NDT&E International. (2020)

[2] Gagliardi V., Bianchini Ciampoli L., D'Amico F., Alani A. M., Tosti F., Battagliere M. L., Benedetto A., Bridge monitoring and assessment by high-resolution satellite remote sensing technologies, Proc. SPIE 11525, SPIE Future Sensing Technologies. 2020. doi: 10.1117/12.2579700

[3] Selvakumaran, S., Plank, S., Geiß, C., Rossi, C., Middleton, C. (2018). Remote monitoring to predict bridge scour failure using Interferometric Synthetic Aperture Radar (InSAR) stacking techniques, Int. J. .Appl. Earth Obs. and Geoinf. 73, 463-470.

[4] Qin X, Liao M., Zhang L., & Yang M., Structural Health and Stability Assessment of High-Speed Railways via Thermal Dilation Mapping with Time-Series InSAR Analysis. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing

How to cite: Gagliardi, V., Bianchini Ciampoli, L., Alani, A., Tosti, F., and Benedetto, A.: Bridge monitoring and deformation time-series analysis by high-resolution Multi-Temporal SAR Interferometry (MT-InSAR) , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15147, https://doi.org/10.5194/egusphere-egu21-15147, 2021.

EGU21-16319 | vPICO presentations | GI2.1

Integrated Health Monitoring of transport assets by ground-based Non-Destructive Technologies (NDTs) and satellite Remote Sensing analysis

Fabrizio D'Amico, Valerio Gagliardi, Chiara Clementini, Daniele Latini, Fabio Del Frate, Luca Bianchini Ciampoli, Alessandro Di Benedetto, Margherita Fiani, and Andrea Benedetto

Bridges and viaducts are exposed to a variety of threats that can affect their operations and structural integrity [1]. Recent unexpected collapses and failures of bridges underline the need for effective structural monitoring, particularly for reinforced concrete structures. In fact, once distress mechanisms are triggered, these can deteriorate faster than the time required for rehabilitation, strengthening, or replacement.

To this extent, it is evident that the monitoring of the actual health conditions of the existing bridges is a priority for asset operators in order to guarantee the structural integrity, the safety of the operations and preventing irreversible damages or even structural collapses.

Within this context, Non-Destructive Testing (NDT) methods such as Ground Penetrating Radar (GPR) and Terrestrial Laser Scanner (TLS) amongst many others have been used for the assessing and monitoring such structures in the past few years[2]. However, topic-related studies [3-4] have demonstrated that stand-alone use of ground-based techniques may not represent a definitive solution to particular major structural issues, such as scour and differential settlements, as these require continuous monitoring and data collection on long-term bases . To that extent, the use of satellite-based remote sensing techniques, such as Synthetic Aperture Radar Interferometry (InSAR), have proven to be effective in detecting displacements with a millimetre accuracy along with transport infrastructures [3-5] and natural terrain considering long periods of observation.

Accordingly, this research aims to present a novel integrated monitoring approach including the use of ground-based technologies (GPR, TLS) and the InSAR techniques over a Maillart arch type bridge: the Viadotto Olivieri in Salerno, (in the South of Italy).

Main objectives of the research  are: (1) to prove the viability of low-frequency and high-frequency GPR systems in providing structural detailing of the bridge-deck at different depths and resolutions; (2) to measure seasonal structural displacements with a millimetre accuracy to detect potential critical issues of the bridge.

The outcomes of this study, under the National Project “EXTRA TN”, PRIN 2017- Prot. 20179BP4SM, demonstrate how multi-temporal InSAR remote sensing techniques can be synergistically applied to complement the traditional ground-based surveys.

 

References

[1] Hosseini Nourzad, S. H. and Pradhan, A. Vulnerability of Infrastructure Systems: Macroscopic Analysis of Critical Disruptions on Road Networks. Journal of Infrastructure Systems, 22(1), 04015014. 2016

[2] D’Aranno, P., Di Benedetto, A., Fiani, M., and Marsella, M.: Remote Sensing Technologies For Linear Infrastructure Monitoring, Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XLII-2/W11, 461–468, https://doi.org/10.5194/isprs-archives-XLII-2-W11-461-2019, 2019.

[3] Bianchini Ciampoli, L., Gagliardi, V., Clementini, et al., Transport Infrastructure Monitoring by InSAR and GPR Data Fusion. Surv Geophys 41, 371–394 (2020). https://doi.org/10.1007/s10712-019-09563-7

[4] Gagliardi V., Benedetto A., Bianchini Ciampoli L., D’Amico F., Alani A., Tosti F., 2020. Health monitoring approach for transport infrastructure and bridges by satellite remote sensing Persistent Scatterer Interferometry (PSI). Proc.SPIE 11534. https://doi.org/10.1117/12.2572395

[5] Bianchini Ciampoli L., Gagliardi V., Calvi A., D’Amico F., Tosti F., Automatic network-level bridge monitoring by integration of InSAR and GIS catalogues. Proceedings of SPIE - The International Society for Optical Engineering, 11059, (2019). DOI: 10.1117/12.2527299

How to cite: D'Amico, F., Gagliardi, V., Clementini, C., Latini, D., Del Frate, F., Bianchini Ciampoli, L., Di Benedetto, A., Fiani, M., and Benedetto, A.: Integrated Health Monitoring of transport assets by ground-based Non-Destructive Technologies (NDTs) and satellite Remote Sensing analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16319, https://doi.org/10.5194/egusphere-egu21-16319, 2021.

GI2.2 – 10 years after the Fukushima accident : Geoscience problems related to massive release of radioactive materials by nuclear accidents and other human activities

The radioactive cesium (134Cs and 137Cs), which originated from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, has remained in the soil and on plants as water-insoluble microparticles (termed as CsMPs) to some extent, and maintained relatively high radioactivity levels in the district. However, it has been reported that the radioactive Cs has been absorbed by plants. To interpret this phenomenon, the authors investigated CsMPs to determine if they become soluble during filtration and dialysis experiments. Moreover, other physical properties, such as mechanical properties and thermal stability, were observed during the course of the relevant experiments. These properties can be obtained by using carbonized charcoal litter with CsMPs. And simple and economic decontamination trials of the soil were performed by sieving after drying and roughly crushing.

How to cite: Tanaka, I., Yamaguchi, A., Kikuchi, K., Niimura, N., Saeki, Y., and Sugihara, M.: Dissolution, Mechanical Properties, and Thermal Stability of Microparticles Containing Radioactive Cesium on Plant Litter Derived from the Fukushima Daiichi Nuclear Power Plant Accident,  and Soil Decontamination Trials , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2976, https://doi.org/10.5194/egusphere-egu21-2976, 2021.

EGU21-3320 | vPICO presentations | GI2.2

Localization of actinide-bearing particles in sediment samples from the Fukushima restriction zone

Aurélie Diacre, Pascal Fichet, Paul Sardini, Jérôme Donnard, Anne-Laure Fauré, Olivier Marie, Katsumi Shozugawa, Michael Susset, Mayumi Hori, Fabien Pointurier, and Olivier Evrard

The Fukushima Dai-Ichi Nuclear Power Plant (FDNPP) accident that occurred in March 2011 released significant quantities of radionuclides into the environment. Ten years after the accident, questions still remain, particularly about the processes that led to the partial core meltdown of reactors 1 and 3. So far, some answers have been provided by the investigation of particles containing caesium (Martin et al., 2020) and sometimes uranium (Ochiai et al., 2018). Indeed, the composition of particles, which were produced and spread at the time of the reactor explosion, reflect the conditions that prevailed in the reactor. Accordingly, the objective of the current research is to develop a method for specifically locating actinide-bearing particles in sediment samples collected in the vicinity of FDNPP. To identify and locate such particles, three already existing methods have been upgraded, including 1) the method of fission tracks already used in the field of non-proliferation studies, 2) the autoradiography through the use of imaging plates that are currently employed in the context of the localization of particles containing radio-caesium and the dismantling of nuclear facilities (Haudebourg and Fichet, 2016), and 3) a real time autoradiography method through the use of the BeaQuant® instrument which has been developed for detecting radioactive particles in biology and geosciences.

In this study, a sediment sample collected nearby FDNPP, which may contain particles containing both radio-caesium and actinides, was selected. This sample was dried and sieved to 63 µm before being processed according to the different analysis protocols.  A quality control sample containing only uranium oxide particles was also analysed, as these particles are devoid of gamma-emitters.

The first results of this comparison of autoradiography methods for the detection of actinide-bearing particles in Fukushima samples will be presented. The method of fission tracks was particularly efficient for detecting both natural and anthropogenic uranium.

The next steps of this study will be to implement this method identified as optimal to isolate and characterise a larger number of particles released by FDNPP. The full characterization of these particles (size, morphology, elemental and isotopic compositions) will provide novel insights to determine their origin and to improve our understanding of their formation processes within the reactors and anticipate their fate in the environment.

References:

Haudebourg, R., Fichet, P., 2016. A non-destructive and on-site digital autoradiography-based tool to identify contaminating radionuclide in nuclear wastes and facilities to be dismantled. J. Radioanal. Nucl. Chem. 309, 551–561. https://doi.org/10.1007/s10967-015-4610-7

Martin, P.G., Jones, C.P., Cipiccia, S., Batey, D.J., Hallam, K.R., Satou, Y., Griffiths, I., Rau, C., Richards, D.A., Sueki, K., Ishii, T., Scott, T.B., 2020. Compositional and structural analysis of Fukushima-derived particulates using high-resolution x-ray imaging and synchrotron characterisation techniques. Sci. Rep. 10, 1636. https://doi.org/10.1038/s41598-020-58545-y

Ochiai, A., Imoto, J., Suetake, M., Komiya, T., Furuki, G., Ikehara, R., Yamasaki, S., Law, G.T.W., Ohnuki, T., Grambow, B., Ewing, R.C., Utsunomiya, S., 2018. Uranium Dioxides and Debris Fragments Released to the Environment with Cesium-Rich Microparticles from the Fukushima Daiichi Nuclear Power Plant. Environ. Sci. Technol. 52, 2586–2594. https://doi.org/10.1021/acs.est.7b06309

 

How to cite: Diacre, A., Fichet, P., Sardini, P., Donnard, J., Fauré, A.-L., Marie, O., Shozugawa, K., Susset, M., Hori, M., Pointurier, F., and Evrard, O.: Localization of actinide-bearing particles in sediment samples from the Fukushima restriction zone, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3320, https://doi.org/10.5194/egusphere-egu21-3320, 2021.

EGU21-14377 | vPICO presentations | GI2.2

3rd model intercomparison projects of atmospheric dispersion model for 137Cs emitted from Fukushima Daiichi Nuclear Power Plant, and application of MIPs' results for usage in an emergency

Hiromi Yamazawa, Yousuke Sato, Tsuyoshi Sekiyama, Mizuo Kajino, Sheng Fang, Arnaud Quérel, Denis Quélo, Hiroaki Kondo, Hiroaki Terada, Masanao Kadowaki, Masayuki Takigawa, Yu Morino, Junya Uchida, Daisuke Goto, Masataka Nakamura, and Yusaku Kiriyama

The 3rd model intercomparison project (MIP) of atmospheric dispersion model targeting on 137Cs emitted from the Fukushima Daiichi Nuclear Power Plant (FDNPP) in March 2011 was conducted (Sato et al. 2020). Nine models participated in the 3rd MIP. All participated models used the identical source term of Katata et al. (2015) and the identical meteorological data (Sekiyama and Kajino, 2020) as in the previous MIP (i.e., 2nd MIP Sato et al. 2018), but finer horizontal grid resolution (1 km) than that of 2nd MIP (3 km) was used for understanding the behavior of atmospheric 137Cs measured in the vicinity of FDNPP. Results of the models elucidated that, as in the 2nd MIP, most of the observed high atmospheric 137Cs concentrations (plumes) were reasonably well simulated by the models, and the good performance of some models cancelled a bad performance of some models when used as an ensemble, which highlights the advantage of the multimodel ensemble. The analyses also indicated that the use of the finer grid resolution (1 km) improved the meteorological field in the vicinity of FNDPP. As a consequence, the atmospheric 137Cs measured near FDNPP was more reasonably reproduced in 3rd MIP than 2nd MIP.

As well as the evaluation of the performance of the model, we examined the usefulness of the results of atmospheric dispersion simulation in an emergency base on the results of 2nd and 3rd MIPs. For the analyses we defined the worst situation as that plume is observed but the model does not simulate it. The analyses reported that the worst situation happened in only 3% of the total calculation period by using the multimodel ensemble, even if the absolute value of the simulated 137Cs in each model was different in the range of factor 3-6. The analyses also indicated that from six to eight models are required for making most of the advantages of the multimodel ensemble.

How to cite: Yamazawa, H., Sato, Y., Sekiyama, T., Kajino, M., Fang, S., Quérel, A., Quélo, D., Kondo, H., Terada, H., Kadowaki, M., Takigawa, M., Morino, Y., Uchida, J., Goto, D., Nakamura, M., and Kiriyama, Y.: 3rd model intercomparison projects of atmospheric dispersion model for 137Cs emitted from Fukushima Daiichi Nuclear Power Plant, and application of MIPs' results for usage in an emergency, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14377, https://doi.org/10.5194/egusphere-egu21-14377, 2021.

EGU21-12433 | vPICO presentations | GI2.2

Bayesian inference and uncertainty quantification for source reconstruction of 137Cs released during the Fukushima accident

Joffrey Dumont Le Brazidec, Marc Bocquet, Olivier Saunier, and Yelva Roustan

In March 2011, large amount of radionuclides were released into the atmosphere throughout the Fukushima Daiichi nuclear disaster. This massive and very complex release, characterized by several peaks and wide temporal variability, lasted for more than three weeks and is subject to large uncertainties. The assessment of the radiological consequences due to the exposure during the emergency phase is highly dependent on the challenging estimate of the source term.

Inverse modelling techniques have proven to be efficient in assessing the source term of radionuclides. Through Bayesian inverse methods, distributions of the variables describing the release such as the duration and the magnitude as well as the observation error can be drawn in order to get a complete characterization of the source.


For complex situations involving releases from several reactors, the temporal evolution of the release may be as difficult to reconstruct as its magnitude. The source term or function of the release is described in the inverse problem as a vector of release rates. Thus, the temporal evolution of the release appears in the definition of the time steps where the release rate is considered constant. The search for the release variability therefore corresponds to the search for the number and length of these successive time steps.

In this study, we propose to tackle the Bayesian inference problem through sampling Monte Carlo Markov Chains methods (MCMC), and more precisely the Reversible-Jump MCMC algorithm.
The Reversible-Jump MCMC method is a transdimensional algorithm which allows to reconstruct the time evolution of the release and its magnitude in the same procedure.

Furthermore, to better quantify uncertainty linked to the reconstructed source term, different approaches are proposed and applied. First, we discuss how to choose the likelihood and propose several distributions. Then, different approaches to model the likelihood covariance matrix are defined.


These different methods are applied to characterize the
137Cs Fukushima source term. We present a posteriori distributions enable to assess the source term and the temporal evolution of the release, to quantify the uncertainties associated to the observations and the modelling of the problem.

How to cite: Dumont Le Brazidec, J., Bocquet, M., Saunier, O., and Roustan, Y.: Bayesian inference and uncertainty quantification for source reconstruction of 137Cs released during the Fukushima accident, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12433, https://doi.org/10.5194/egusphere-egu21-12433, 2021.

EGU21-5134 | vPICO presentations | GI2.2

Modeling study of the atmospheric transport of radioactivity after wildland fires and a dust storm in the Chernobyl Exclusion Zone in April 2020

Mykola Talerko, Tatiana Lev, Ivan Kovalets, Mark Zheleznyak, Yasunori Igarashi, Serhii Paskevych, Volodymyr Kashpur, and Serhii Kireev

In April 2020, the largest forest fire occurred in the Chernobyl Exclusion Zone (ChEZ) in its history. The results of modeling the atmospheric transport of radioactive aerosols released into the atmosphere as a result of wildland fires in the ChEZ and around it are presented. The atmospheric transport model LEDI, developed at the Institute for Safety Problems of NPPs, and the Atmospheric Dispersion Module of the real -time online decision support system for offsite nuclear emergency RODOS, which development was funded by the EU, were used. The 137Cs activity concentration in the surface air is calculated on a regional scale (in Ukraine) and a local scale (within the ChEZ). The 137Cs activity in the surface air of Kyiv (115 km from the ChEZ borders) is found to have reached 2–4 mBq m−3 during the period April 3–20. The modeling results are generally consistent with measured data pertaining to radioactive contamination in Kyiv, within the ChEZ, and areas around four operating nuclear power plants in Ukraine.

A method for estimating the radionuclide activity emissions during wildland fires in radioactively contaminated areas is proposed. This method is based on satellite data of the fire radiative power (FRP), the radionuclide inventory in the fire area, and an emission factor for radioactive particles. A method was applied for forest fires in the ChEZ in April 2020. Preliminary estimations of an emission factor are made using FRP values obtained from NASA's MODIS and VIIRS active fire products.

On April 16, 2020, a strong dust storm was observed in the ChEZ, which coincided with the period of intense wildland fires. The additional 137Cs activity raised by the dust storm from burned areas in the meadow biocenoses was estimated to be about 162 GBq, i.e. up to 20% of the total activity emitted into the air during the entire period of forest fires on April 3-20, 2020. According to the modeling results, during April 16-17, the input of resuspension of radioactive particles due to a dust storm was up to 80-95% of the total 137Cs activity in the surface air near the Chernobyl NPP. In Kyiv, this value decreased to only about 4%.

The total effective dose to the population of Kyiv during the fire period is estimated to be 5.7 nSv from external exposure and the inhalation of 137Cs and 90Sr, rising to 30 nSv by the end of 2020. This is about 0.003% of the annual permissible level of exposure of the population. A committed effective dose up to 200-500 nSv is estimated for the personnel of the Chernobyl NPP from the radioactive aerosol inhalation during the 2020 forest fires, which is not more than 0.05% of the established control levels of internal exposure for them.

How to cite: Talerko, M., Lev, T., Kovalets, I., Zheleznyak, M., Igarashi, Y., Paskevych, S., Kashpur, V., and Kireev, S.: Modeling study of the atmospheric transport of radioactivity after wildland fires and a dust storm in the Chernobyl Exclusion Zone in April 2020, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5134, https://doi.org/10.5194/egusphere-egu21-5134, 2021.

The atmospheric release of radionuclides is a crucial potential hazard to public health. Its release rate is vital in assessing the international environmental risk of atmospheric radionuclide leaks and conducting nuclear emergency preparedness. However, according to the radionuclide leaks such as the Fukushima Daiichi accident and the recent iodine-131 and ruthenium-106 releases in 2017, the release rate cannot be directly measured or derived in a forward way, but can only be inversely estimated by comparing the environmental measurements with a model-predicted plume, a technique often referred to as source inversion. However, such inversion is vulnerable to the inevitable plume biases, including the plume range (i.e. the area of positive model predictions) and transport pattern in radionuclide transport modeling, leading to inaccurate source estimates and risk assessment.

This paper describes an automated method that estimates the release rate while comprehensively correcting plume biases. By using the spatial correlation matrix, the predicted plume can spread over a broader area, thus covering the potential range of the true plume. Then, the difficult task of direct plume adjustment is simplified to tuning the predictions inside a correlation-adjusted plume. Based on this, the previous joint method can work efficiently to estimate the release rate while simultaneously refining the predictions inside the adjusted range, correcting both the plume range and the transport pattern. An ensemble-based algorithm is proposed to automatically calculate the spatial correlation in order to execute this method. With this algorithm, SERACT can accomplish realistic and robust source estimation without manual adjustment on any parameters.

The proposed method SERACT is validated with the two wind tunnel experiments based on a real Chinese nuclear power plant site, and the site features highly heterogeneous topography and dense buildings. In this paper, two radionuclide transport models with mild and severe plume biases respectively are used to assess the adjustment efficiency of SERACT, including source estimation and plume distribution. Its performance is compared with that of the standard approach and a recent state-of-the-art method. Its sensitivity to the number and quality of measurements, and the selection of autocorrelation scales is also investigated.

The results demonstrate that SERACT corrects the plume biases with high accuracy (Pearson’s Correlation Coefficient=1.0000, Normalized Mean Square Error≤1.03×10−3) and reduces the estimation error by nearly two orders of magnitude at best. In addition, SERACT exhibited stable performance in all the validation tests and gave the lowest error levels with various numbers and quality of measurements. With fully automated parameterization, its performance is close to that obtained with the optimal autocorrelation scale in all test cases. These results indicate that SERACT is robust in various inversion cases and is able to serve as a general remediation to the long-standing imperfect modeling issue in source inversion.

How to cite: Zhuang, S. and Fang, S.: Simultaneous release rate estimation and modeled plume bias correction for atmospheric radionuclide emissions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-114, https://doi.org/10.5194/egusphere-egu21-114, 2021.

EGU21-8129 | vPICO presentations | GI2.2