G4.3 | Gravity and magnetic field studies - methods and applications
EDI
Gravity and magnetic field studies - methods and applications
Co-organized by EMRP2/GD6
Convener: Jörg Ebbing | Co-conveners: Carla Braitenberg, Alexandra Guy, Bart Root, Mikhail Kaban
Orals
| Thu, 18 Apr, 16:15–18:00 (CEST)
 
Room D1
Posters on site
| Attendance Wed, 17 Apr, 16:15–18:00 (CEST) | Display Wed, 17 Apr, 14:00–18:00
 
Hall X2
Orals |
Thu, 16:15
Wed, 16:15
The session is dedicated to the processing and modelling of gravity and magnetic field data related to spatial and temporal variations at all scales. This includes studies on modern processing and interpretation methods (e.g. including machine learning) as well as forward and inverse modelling case studies. Of special interest are studies dedicated to the crustal or lithospheric structure by integrating gravity and magnetic methods with other geophysical data (e.g. petrophysics, seismic) or combining data from terrestrial, airborne and satellite missions.

Orals: Thu, 18 Apr | Room D1

Chairpersons: Jörg Ebbing, Carla Braitenberg
16:15–16:20
16:20–16:40
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EGU24-11380
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ECS
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solicited
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On-site presentation
Michael Field, Emma MacKie, Lijing Wang, and Atsuhiro Muto

Sub-ice-shelf bathymetry controls the delivery of warm water to the ice-shelf bottom in West Antarctica, making the bathymetry beneath ice shelves in the Amundsen Sea critical inputs to ice-sheet and ocean models. Previous estimates of the bathymetry have often used deterministic inversion frameworks or do not account for the non-uniqueness of the inverse problem, and ultimately lack robust uncertainty quantification. To provide more robust and reproducible bathymetry models, we implement a random walk Metropolis-Hastings Markov Chain Monte Carlo (MCMC) inversion approach, which iteratively generates model perturbations using random Gaussian fields and forward models the gravity disturbance of proposed bathymetry models. After convergence, our approach samples the posterior distribution allowing for estimation of the mean and variance of the bathymetry while providing realistic models of the sub-ice-shelf bathymetry. An ensemble of bathymetry models can then be used in ice-sheet and ocean simulations to propagate the uncertainty in bathymetry to dynamic ice processes, resulting in better uncertainty quantification of future sea-level rise. In addition to providing more robust bathymetry models, this work provides a step forward in the reproducibility of geophysical inversions by leveraging the growing open-access geoscientific computing ecosystem of Python.

How to cite: Field, M., MacKie, E., Wang, L., and Muto, A.: Gravity inversion of sub-ice shelf bathymetry in West Antarctica using a geostatistical Markov Chain Monte Carlo approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11380, https://doi.org/10.5194/egusphere-egu24-11380, 2024.

16:40–16:50
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EGU24-12510
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ECS
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Highlight
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On-site presentation
Megan Kerr, Duncan Young, Weisen Shen, Gregory Ng, Shivangini Singh, Dillon Buhl, Jamin Greenbaum, Shuai Yan, and Donald Blankenship

Because sedimentary basins may exert considerable control over ice sheet dynamics and basal heat flow, it is vital to constrain the extent, thickness, and level of consolidation of sediments throughout the continent and at local scales. Until recently, the South Pole Basin (SPB), situated between the Gamburtsev Subglacial Mountains, the Transantarctic Mountains, and Recovery Subglacial Highlands, has been one of Antarctica's least-explored regions. Previous studies based on seismic and machine learning models, including those by Baranov & Morelli (2023) and Li et al. (2022), have characterized SPB as a sedimentary basin with sediment thicknesses exceeding 1 km. Conversely, a seismic study conducted by Zhou et al. (2022) identifies SPB as a region with little to no sedimentary rock. A lack of dense geophysical data as well as the inherent difficulty of studying geology beneath the Antarctic Ice Sheet introduced a large amount of uncertainty into these assessments. Recent airborne radar, gravity, and magnetics data collected by the Center for Oldest Ice Exploration (COLDEX) has revealed two distinct geomorphological provinces within South Pole Basin: the southern portion of SPB which exhibits relatively smooth, reflective bedrock, while the northern SBP manifests as much rougher terrain. The abrupt boundary between Inner and Outer SPB is associated with the onset of subglacial melting, inferred from a rapid thinning of the basal layer, decreased ice sheet surface slope, and presence of subglacial lake-like features. In addition to surficial differences, these provinces are marked by distinct free-air, Bouguer, and isostatic gravity signatures. A large, arc-shaped magnetic high parallel to Recovery Subglacial Highlands cuts across SBP, facilitating a robust depth to basement analysis and providing constraints for gravity inversions. By integrating COLDEX data with previous airborne surveys and newly collected seismic data, we offer a revised geological interpretation of the South Pole Basin and discuss its tectonic history, potential for groundwater storage, and the preservation of ancient ice in this region.

How to cite: Kerr, M., Young, D., Shen, W., Ng, G., Singh, S., Buhl, D., Greenbaum, J., Yan, S., and Blankenship, D.: Are there thick sediments within South Pole Basin? Investigating the lithology of SPB using COLDEX airborne geophysics , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12510, https://doi.org/10.5194/egusphere-egu24-12510, 2024.

16:50–17:00
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EGU24-2837
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ECS
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On-site presentation
Mikhail Ginga, Jörg Ebbing, Antonia Stefanie Ruppel, Andreas Läufer, and Graeme Eagles

Topography and physical conditions at the base of the Antarctic ice sheet are critical inputs for studies of its present and future ice discharge, and of subglacial geology and hydrology. Airborne gravity and magnetic data, especially when interpreted jointly can help us to link the geology from outcrops towards the coastal areas to unknown subglacial regions further inland. Here we use airborne geophysical data obtained during the joint AWI-BGR campaign WEGAS/GEA between 2015 and 2017 in central Dronning Maud Land (DML) as input for a novel joint inversion scheme. With regard to Gondwana reconstruction, this region is critical because it hosts the ice-covered Forster Magnetic Anomaly, a prominent lineament crossing central DML for some 100s of kilometers south of the main mountain chain. This lineament, originally interpreted as the main pan-African suture of East and West Gondwana, likely represents the eastern margin of Kalahari and its boundary to the Tonian Oceanic Arc Super Terrane (TOAST). In the inversion using the software jif3D, sources of the gravity and magnetic field are combined through a coupling method which decreases the variation of information (VI), so data misfit and model dissimilarity are minimized simultaneously. The model results can be classified in geologically meaningful provinces by applying cluster analysis based on machine learning. Our joint inversion approach improves previous interpretations and sheds light on the crustal architecture of the study area, contributing to further studies on the interaction between the ice sheet and the underlying solid earth.

How to cite: Ginga, M., Ebbing, J., Ruppel, A. S., Läufer, A., and Eagles, G.: Joint inversion of airborne gravity and magnetic data for the crustal structure in central Dronning Maud Land, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2837, https://doi.org/10.5194/egusphere-egu24-2837, 2024.

17:00–17:10
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EGU24-10299
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ECS
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On-site presentation
Bjørnar Dale, Sebastian Bjerregaard Simonsen, Ove Christian Dahl Omang, Tim Enzlberger Jensen, and René Forsberg

Airborne gravimetry provides gravity observations of higher spatial resolution than what can be obtained from satellite gravity field measurements, and together with terrestrial measurements they augment the satellite observations to determine high-resolution geoid models. Satellite altimetry in coastal and ice-covered regions is known to have significant errors. We use modern strapdown gravimetry for the surveys and compare the indirect method, using Kalman filtering, and the direct filtering method for the processing. We present the result of strapdown gravimetry for two airborne campaigns conducted in Antarctica 2022 and Norway 2023. During both campaigns the sensors used were an iMAR navigation-grade inertial measurement unit together with a geodetic GNSS receiver.

The 2022 campaign covered part of the sea-ice covered Weddell Sea and was surveyed as a piggyback activity as part of the ESA CRYO2ICE and NERC DEFIANT 2022 Antractica campaign. The 2023 airborne campaign was carried out in the coastal region of Norway near Trondheim. In both areas the data were compared to satellite altimetry and other gravity data from ship or airborne surveys. Both campaigns show improvements in spatial resolution and accuracy of the new mGal-level airborne gravimetry data when compared to satellite altimetry and older marine gravity observations.

How to cite: Dale, B., Bjerregaard Simonsen, S., Christian Dahl Omang, O., Enzlberger Jensen, T., and Forsberg, R.: Satellite gravity validation by new airborne gravimetry in coastal regions of Antarctica and Norway, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10299, https://doi.org/10.5194/egusphere-egu24-10299, 2024.

17:10–17:20
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EGU24-14771
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ECS
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On-site presentation
Agnes Dakota Wansing, Jörg Ebbing, Max Moorkamp, and Björn Heincke

The surface geology of Greenland is only known along the ice-free coast. The remaining 80% of Earth's largest island are covered by ice that masks the surface geology and makes direct observation nearly impossible. Interpolation of the known coastal geology over the inland ice, combined with expert knowledge, can provide a first, but not well-constrained picture. In contrast, the surface geology in Scandinavia is well-studied. The formerly adjacent northeastern part of Greenland belongs to the same Caledonian orogeny and is expected to be somewhat similar to Scandinavia. Therefore, we use Scandinavia as a case study to set up a workflow of joint inversion of potential field data to find physical relations for the known geological structure and apply this workflow to NE Greenland.

Results from individual inversion of potential field data are non-unique and have limited depth resolution. Combining gravity and magnetic data in a joint inversion can minimise the non-uniqueness and improve the depth resolution. The coupling furthermore creates comparable anomaly patterns for both inverted parameters. As coupling method, a variation of information (VI) constraint is used in the inversion. The VI creates representative parameter relationships where different branches reflect the numerous combinations of density and susceptibility for various rock types. Thus, the inverted parameter relationship can be used to map the surface geology.

Crucial parts in the workflow setup are how deeper sources are handled for the gravity data and at which resolution and height the magnetic data are required.  The simultaneous analysis of the well-studied surface geology in Scandinavia helps to verify the analysis, providing higher confidence in the resulting sub-ice geology for NE Greenland.

How to cite: Wansing, A. D., Ebbing, J., Moorkamp, M., and Heincke, B.: Joint inversion of potential field data to unmask sub-ice geology, from a case study in Scandinavia to application in NE Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14771, https://doi.org/10.5194/egusphere-egu24-14771, 2024.

17:20–17:30
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EGU24-14351
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ECS
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On-site presentation
Ke Wang and Dikun Yang

Joint inversion can utilize multiple geophysical datasets to supplement or enhance the information on subsurface structures, improve the resolution and certainty of recovered subsurface structures, and provide broad prospects for various geophysical application scenarios. Model coupling is crucial in joint inversion, and there are two main coupling methods based on structural similarity and petrophysical information. These two coupling methods have their own advantages and disadvantages. The structural similarity-based coupling method can obtain structurally similar models without prior information, but the assumption of structural similarity between models is not always valid. The petrophysics-based coupling method provides finer constraints on physical property values, and its difficulty lies in acquiring petrophysical information, which is usually imprecise and incomplete in the inversion region. Joint inversion using a single model coupling approach is insufficient to face complex joint inversion situations. Combining the two coupling methods can complement the structural similarity of the model in the inversion of incomplete petrophysical information.

We develop a novel joint inversion method based on the extended alternating direction method of multipliers (eADMM), which is compatible with multiple model coupling methods and reduces non-uniqueness and uncertainty more effectively. Multiple model coupling methods are contained in an indicator function, which requires the model to satisfy specific mathematical sets, allowing the various models to satisfy arbitrary relationships and ranges. The inequality constraints and linear and nonlinear relational equations extracted from the petrophysical information are expressed directly in mathematical sets, and the structural similarity coupling is implemented by a constraint set that requires a cross-gradient of zero between models. The solution of the indicator function in the eADMM framework is converted into a projection function, and we develop corresponding projection algorithms for multiple constraint sets of both model coupling strategies. The constraint sets are also spatially flexible. Regions with complete petrophysical information and regions requiring increased structural similarity can be constrained by the corresponding sets, respectively.

We apply the method to gravity and magnetic data to test its performance. We compare the performance of our method with that of the joint inversion using a single coupling method for incomplete petrophysical information, including petrophysical information for partial regions and partial geologic units. Synthetic examples show that regions and geologic units with known petrophysical information are recovered with accurate geometric boundaries and physical property values closer to the true values, and structural similarity coupling provides structural information for unknown regions or geologic units, recovers more accurate geometric structures and reduces model uncertainty. The new joint inversion method provides higher resolution models than the traditional joint inversion method, and the inversion results are closer to the true model.

How to cite: Wang, K. and Yang, D.: joint inversion of gravity and magnetic data with petrophysical and structural coupling constraints using indicator functions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14351, https://doi.org/10.5194/egusphere-egu24-14351, 2024.

17:30–17:40
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EGU24-1405
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ECS
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Virtual presentation
Arka Roy, Rajat Kumar Sharma, Dharmadas Jash, and Tomson J Kallukalam

Precise determination of Moho topography holds paramount importance in advancing our comprehension of Earth's structural characteristics, geodynamic phenomena, and the exploration of resources. This study introduces an innovative methodology employing conditional Generative Adversarial Networks (cGAN) to unveil Moho topographies from observed gravity anomalies. To address the scarcity of real Moho datasets for training the cGAN model, we meticulously generated a comprehensive set of quasi-realistic synthetic training data using the FFT filtering technique. The forward estimation of gravity anomalies, arising from synthetic Moho topographies, was assessed through spherical prism-based gravity modeling. These estimated anomalies served as input data for the training of the cGAN model. For evaluating the efficacy of our developed cGAN algorithm in deriving Moho architecture, we conducted a comparative analysis against a conventional inversion scheme. This assessment utilized various synthetic datasets and a real case study in Southern Peninsular India, renowned for its geological diversity and ancient continental tectonic blocks. The established Bott's inversion scheme was employed as a benchmark to validate the Moho surface estimation obtained through the Deep Learning approach. To mitigate the impact of diverse factors such as topography, bathymetry, sediments, crustal and mantle heterogeneities, observed gravity anomalies underwent meticulous corrections using spherical prism-based forward gravity modeling for real case studies. The gravity contribution exclusively associated with the pure Moho was subsequently inverted using both the cGAN and traditional Bott's inversion schemes. Crucial hyperparameters, including the mean Moho depth and density contrast between the crust and mantle, were determined by utilizing seismic constraints. Our results underscore the potential of the cGAN and spherical prism-based gravity modeling approach in accurately predicting Moho topography. This study provides valuable insights into high-resolution Earth's Moho architecture and contributes to advancing our understanding of geodynamic processes, facilitating resource exploration endeavours with reduced computational demands.

How to cite: Roy, A., Sharma, R. K., Jash, D., and Kallukalam, T. J.: Innovative Insights into Earth's Interior: Moho Topography Estimation using Conditional Generative Adversarial Networks from Observed Gravity Anomalies , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1405, https://doi.org/10.5194/egusphere-egu24-1405, 2024.

17:40–17:50
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EGU24-9258
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ECS
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On-site presentation
Zhixin Xue, Dongmei Guo, Jian Fang, and Huiyou He

The Moho interface is an important parameter for describing the structure and morphology of the Earth's crust, and it is of significant importance in the study of the formation and evolution of the crust and mantle, as well as deep-seated dynamic processes (Stern et al., 2018). Existing Moho models derived from seismic data often suffer from inaccuracies due to irregular distribution and regional imbalances of seismic data. However, with the development of gravity satellite technology, high-precision satellite gravity data has injected new vitality into the study of lithospheric tectonic features and crustal evolution. In this study, constrained by seismic data (Li et al., 2013; Zhang et al., 2021), we utilized an improved regularized Bott method (Uieda et al., 2017) to invert high-precision satellite gravity data and obtained a high-precision unified Moho depth model for the East Asian region, encompassing both land and sea areas. The research results show that the Moho depth model exhibits a continuous increase in depth from east to west, and its overall distribution in the horizontal direction is non-uniform, displaying distinct regional block features. This paper provides a high-resolution and high-precision Moho model for studying the evolution of the East Asian continental tectonics and plate interactions, and further discusses the macrostructural framework and geological implications of East Asia.

References

Li Y Gao M, Wu Q. Crustal Thickness Map of the Chinese Mainland from Teleseismic Receiver Functions [J]. Tectonophysics, 2013, 611.

Stern, Robert, J, et al. Continental crust of China: A brief guide for the perplexed [J]. Earth Science Reviews the International Geological Journal Bridging the Gap Between Research Articles & Textbooks, 2018.

Uieda L, Barbosa V. Fast nonlinear gravity inversion in spherical coordinates with application to the South American Moho [J]. Geophysical Journal International, 2016.

Zhang J , Yang G , Tan H , et al. Mapping the Moho depth and ocean-continent transition in the South China Sea using gravity inversion [J]. Journal of Asian Earth Sciences, 2021, 218(3–4):104864.

How to cite: Xue, Z., Guo, D., Fang, J., and He, H.: Moho Depth Model and Structural Characteristics of China and Adjacent Regions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9258, https://doi.org/10.5194/egusphere-egu24-9258, 2024.

17:50–18:00
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EGU24-397
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ECS
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On-site presentation
Nedim Gökhan Aydın and Turgay İşseven

This study employs gravity modelling to investigate the subsurface geometry of a pull-apart basin located in Elazığ, Turkey. The study area is situated along the East Anatolian Fault Zone—a major active system that recently produced two devastating M7.0+ earthquakes at Kahramanmaraş in February 6, 2023.

Recently collected gravity data, comprising approximately 600 data points from Sivrice and Gezin provinces, form the basis of our investigation. Preliminary examinations show that the gravity anomalies in Gezin are notably lower than those in Sivrice, suggesting a deeper basement for the former. We aimed to estimate the subsurface model using a proprietary computer program. Given the known different geological units with constant density contrasts, the program was employed to deduce their geometry up to a maximum depth of 350 meters in 2D. A total of 16 sections were modeled—8 each for Sivrice and Gezin provinces—yielding RMS values consistently below 0.1 mGals. Next, quasi-3D and 3D models were prepared for Talwani models at Sivrice and Gezin. We assumed the geometry beneath Lake Hazar to be similar to the bathymetry of the lake, assigning sediment thickness to estimate the basement in this part. The individual models were then integrated into a full 3D representation of the geometry of the basin.

Our findings suggest that the pull-apart basin situated here is in its extinction phase, with pull-apart tectonics no longer active, and only strike-slip movement along main East Anatolian Fault is observed. Notably, slips along the main fault have impacted the basement geometry. This study contributes valuable insights into the current state of the basin, emphasizing the importance of 3D modelling in unraveling the complexities of pull-apart basins.

How to cite: Aydın, N. G. and İşseven, T.: Gravity Modelling of a Pull-Apart Basin in Elazığ, Turkey: Unraveling the 3D Basement Geometry (Preliminary Results), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-397, https://doi.org/10.5194/egusphere-egu24-397, 2024.

Posters on site: Wed, 17 Apr, 16:15–18:00 | Hall X2

Display time: Wed, 17 Apr 14:00–Wed, 17 Apr 18:00
Chairpersons: Bart Root, Mikhail Kaban
X2.1
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EGU24-6402
György Hetényi, Ludovic Baron, Matteo Scarponi, Shiba Subedi, Konstantinos Michailos, Fergus Dal, Anna Gerle, Benoît Petri, Jodok Zwahlen, Antonio Langone, Andrew Greenwood, Luca Ziberna, Mattia Pistone, Alberto Zanetti, and Othmar Müntener

The Balmuccia peridotite exposes relatively fresh mantle rocks at the Earth’s surface, and as such it is of interest for geologists and geophysicists. The outcrop is a kilometre-scale feature, yet its extent at depth is insufficiently imaged. Our aim is to provide new constraints on the shape of the density anomaly this body represents, through 3D gravity modelling. In an effort to avoid personal or methodology bias, we hereby launch an invitation and call for participative modelling. We openly provide all the necessary input data: pre-processed gravity data, geological map, in situ rock densities, and digital elevation model. The expected inversion results will be compared and jointly analysed with all participants. This approach should allow us to conclude on the shape of the Balmuccia peridotite body and the associated uncertainty. This crowd effort will contribute to the site surveys preparing a scientific borehole in the area in frame of project DIVE. The full description, the dataset, as well as the tentative timeline can be found at https://zenodo.org/records/10390437

How to cite: Hetényi, G., Baron, L., Scarponi, M., Subedi, S., Michailos, K., Dal, F., Gerle, A., Petri, B., Zwahlen, J., Langone, A., Greenwood, A., Ziberna, L., Pistone, M., Zanetti, A., and Müntener, O.: Participative gravity-modelling challenge to constrain the Balmuccia peridotite body (Ivrea-Verbano Zone, Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6402, https://doi.org/10.5194/egusphere-egu24-6402, 2024.

X2.2
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EGU24-17176
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ECS
Matteo Scarponi and Thomas Bodin

The Western Alps constitute a complex and heterogeneous orogenic system, generated by the continental collision between the European and Adriatic tectonic plates. Three main tectonic domains can be identified across local to regional scales, based on geophysical and geological observations: the European and Adriatic domains, and the high-density, high-velocity anomaly known as Ivrea geophysical body (IGB). Despite being one of the best-studied collisional systems in the world, the 3D Western Alpine lithosphere and its along-arc compositional and structural variations are still subjects of investigations.

 

In this framework, we exploit the inherently-3D information provided by gravity data. In particular, we set up a 3D Bayesian joint inversion of Bouguer gravity anomaly and surface wave dispersion data, to obtain a new 3D ρ-vS model of the Western Alpine lithosphere. We benefit from the Bouguer anomaly map by Zahorec et al. (2021), obtained by homogeneous processing of gravity data across the Alpine domain, and from seismic data recorded by permanent and temporary seismic networks: e.g. IvreaArray, AlpArray (Hetényi et al. 2017, 2018), CIFALPS I and II (e.g. Paul et al. 2022).

 

We perform 3D forward gravity modeling by discretizing the study area in unitary volumes of constant density (voxels), accounting for spherical Earth structure and surface topography. The gravity effect of each voxel is pre-computed, and then only needs to be scaled with density during the inversion. This significantly decreases the computational cost of the forward model, and thus allows us to explore the parameter space with Monte Carlo sampling. We use a Bayesian framework and implement a Markov chain Monte Carlo (McMC) algorithm. We test different types of  parameterizations to reduce the non-uniqueness of gravity inversion. We plan to jointly invert gravity with surface wave dispersion data, providing complementary information on vS. Finally, existing receiver function studies (e.g. Monna et al. 2022, Paul et al. 2022, Michailos et al. 2023) provide prior information on crustal and lithospheric geometry.


We expect to obtain a new 3D ρ-vS model for the Western Alpine crust and lithosphere. This will provide new information on the European-Adriatic collision boundary, together with the IGB structure, and their three-dimensional variation along the orogen. The new model will be also useful to constrain rock composition, upon comparison with the geological observations at the surface.

How to cite: Scarponi, M. and Bodin, T.: Bayesian Joint Inversion of Bouguer Gravity and Surface Wave data: application to the Western Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17176, https://doi.org/10.5194/egusphere-egu24-17176, 2024.

X2.3
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EGU24-4560
Stanisław Mazur

In Western Europe, the Variscan belt contacts Avalonia along the Rhenohercynian Suture, a result of Early Carboniferous continental collision. Moving east of the Harz Mts., the Rhenohercynian suture disappears beneath a thick sedimentary sequence of the Permian-Mesozoic basin. Its extension is either truncated by major NW-SE strike-slip faults like the Elbe, Odra, or Dolsk faults or bends under the cover of a thick sedimentary succession. The extension of Avalonia into Poland is challenging to determine, with the thinned margin of Baltica considered the substratum of the Permian-Mesozoic basin. Deep seismic soundings show that the thinned margin of Baltica reaches the NW-SE oriented Dolsk or Odra fault, potentially bringing the crust of Baltica into direct contact with the crust of the Variscan internides of the Bohemian Massif. Along the Dolsk fault, there is the two-layered, low-velocity Variscan crust in the SW that contacts the three-layered Baltica crust. The geometry of this contact remains unknown, but the lower, high-velocity crust of Baltica may extend southwest to the Odra fault. In the basement of the sedimentary sequence between the Dolsk and Odra faults, low-grade metamorphosed phyllites with a metamorphic age of approximately 360 Ma are found. They apparently represent a fragment of Variscan metamorphic nappes.

The Variscan front is oriented NE-SW in Western Europe, but in Poland, it bends by 90° to the NW-SE direction, continuing to the border of Ukraine. In southeastern Poland, the front enters the slope of the East European Platform, constituting an undisputed example of a direct contact between the Variscan belt and Baltica. If the geometry of the Variscan front reflects the structure of the orogen, the edge of Baltica must have initially played the role of a transform margin with a right-lateral displacement. NW-SE strike-slip faults, parallel to this margin, truncated the Rhenohercynian and other Variscan sutures from the NE. The following accretion event resulted in NE-SW shortening, either thin-skinned, leading to folding of the external fold-and-thrust belt, or thick-skinned, resulting in the emplacement of the Variscan nappe stack on the Baltica margin.

The last folding of external Variscides in Poland occurred around 305 Ma and was immediately followed by the emplacement of a large igneous province at the Carboniferous to Permian transition. The centre of magmatism was in NE Germany, the area of greatest crustal thinning. The origin of the igneous province was linked to plate boundary forces leading to extension and continental rifting. The latter produced the Mid-Polish trough, an elongated continental rift running NW-SE parallel to the Teisseyre-Tornquist zone. Permian rifting further attenuated the Baltica margin and, jointly with coeval magmatism, reshaped the margin of Baltica masking its contact with the Variscan belt. Toward the east, the continuity of the Variscan internides was disrupted by early Mesozoic rifting in the area of the present-day Carpathians.

How to cite: Mazur, S.: From Carboniferous convergence to Permian continental rifting – the interaction of Baltica with the Variscan belt of Europe at the time of the Pangaea assembly, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4560, https://doi.org/10.5194/egusphere-egu24-4560, 2024.

X2.4
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EGU24-6228
Hans-Jürgen Götze, Ronja Strehlau, Denis Anikiev, Anke Dannowski, and Magdalena Scheck-Wenderoth

This interdisciplinary study describes the integration of gravity field analysis, curvature techniques and various spatial applications. The data are based on land-based Free Air and Bouguer gravity data from the AlpArray Gravity Research Group, complemented by recent satellite missions. New seismic and seismological data from the AlpArray initiative and the German MB-4D Priority Program were used as independent boundary conditions for the 3D modeling and inversion of the gravity data. Prior to this modeling, Euler deconvolution, terracing/clustering techniques, and advanced filtering methods were employed to reveal intricate details of the region's gravitational signatures. For example, a distinct zoning of gravity is observed in the central part of the Ligurian Sea, pointing to traces of past rifting processes. Analysis of various curvature parameters (e.g., dip-, min-, max- and shape-curvature) of the processed gravity fields, in particular gradients and residual fields support the identified zonation of the gravity fields, which reflect the geological structures in the crust. The final 3D modeling of the Ligurian Sea area is based on a previous density model of the entire Alpine region and includes density distribution of the upper mantle. These densities were derived from tomographic velocity models, accounting for petrology, temperature, and pressure. Additional information of the upper crust was obtained from the refraction seismic results of the LOBSTER project, offering a comprehensive understanding of spatial phenomena. Calculations of the gravitational potential energy (GPE) provide additional information on local stresses, facilitating a deeper understanding of the flexural rigidity in the area. By elucidating the relationship between processing techniques and 3D modeling, this work advances interdisciplinary interpretation crucial for geological studies in the Ligurian offshore area.

How to cite: Götze, H.-J., Strehlau, R., Anikiev, D., Dannowski, A., and Scheck-Wenderoth, M.: Harnessing Modern 3D Gravity Analysis Techniques: A Study of the Ligurian Offshore Area, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6228, https://doi.org/10.5194/egusphere-egu24-6228, 2024.

X2.5
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EGU24-2511
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ECS
An Iterative Algorithm for Predicting Seafloor Topography from Satellite Altimetry Gravity Data
(withdrawn after no-show)
Bang An and Jinhai Yu
X2.6
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EGU24-17112
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ECS
Zhourun Ye, Jingyu Bu, and Nico Sneeuw

Through Stokes kernel function and gravity anomaly, it is possible to calculate the gravity gradient disturbance on the geoid and its external space. For this Stokes’ integral expression, we apply Laguerre wavelet numerical integration to improve the accuracy of its computational results. Meanwhile, compute unified device architecture (CUDA) is used to implement parallel computing on the Graphic Processing Unit (GPU) for speeding up. The full tensors of gravity gradient in the experimental ocean area with 3°×2°are computed. Compared to serial computing, its computing acceleration ratio can be more than 10 times faster. The results of the vertical gravity gradient are compared and validated from the public model from the University of California San Diego.

How to cite: Ye, Z., Bu, J., and Sneeuw, N.: Application of numerical integration and CUDA parallel in the calculation of ocean gravity gradient, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17112, https://doi.org/10.5194/egusphere-egu24-17112, 2024.

X2.7
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EGU24-5638
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ECS
Comparative Study on Topography Prediction Using Gravity Anomalies and Gravity Gradient Anomalies
(withdrawn)
Yuwei Tian, Huan Xu, and Jinhai Yu
X2.8
|
EGU24-4845
Dongmei Guo

The South China Sea, situated at the convergence of the Tethys and Pacific tectonic domains, holds immense geological significance due to its interaction with multiple tectonic plates (Hall 2002; Hayes and Nissen 2005; Metcalfe 2011). With its abundant sedimentary basins, the region is of paramount importance for geological and structural studies, particularly in relation to its potential for oil and gas resources. In this study, we propose the utilization of satellite gravity data to analyze the tectonic structure of the South China Sea, focusing on three key areas:

1. High-resolution construction of gravity gradient anomalies and fault identification: By integrating Fast Fourier Transform algorithms with satellite gravity anomalies and high-resolution terrain elevation data, we obtaina comprehensive dataset of full tensor gravity gradient information. Through spatial analysis of this data, we successfully identify 17 significant and deep faults, as well as partition the study area into 9 distinct tectonic units characterized by well-defined geological structures.

2. Moho Depth Determination and Interpretation: Employing an improved regularization Bott's method, we determine the Moho depth using information obtained from sonar-buoy detection and submarine seismograph detection profiles. Regularization parameters are introduced to ensure the smoothness of the inversion results. By analyzing the distribution characteristics of the Moho and its relationship with tectonic units, we conduct a comprehensive analysis to comprehend the coupling between shallow and deep structures. The resultsreveal distinct regional characteristics in the depth distribution of the Moho surface in the South China Sea, shedding light on the distribution of continental crust, oceanic crust, and the ocean-continent transition zone.

3. Comprehensive Geophysical Analysis: We employ a combination of seismically constrained Moho undulation, gravity data, gravity gradient anomalies, and unconstrained 3D correlation imaging to investigate the crustal structure of the South China Sea. Integrating various geophysical datasets, we gain a deeper understanding of the distribution of continental crust, oceanic crust, and transitional crust within the region. Notably, the results shows that the trench-island arc-back arc basin systemplays a pivotal role in the active continental margin of the Western Pacific. This comprehensive analysis provides valuable insights into the tectonic dynamics and geological processes occurring in the South China Sea region.

*This study was supported by y the Basic Frontier Science Research Program of the Chinese Academy of Sciences (No. ZDBS-LY-DQC028).

Reference:

Hall, R. (2002). Cenozoic geological and plate tectonic evolution of SE Asia and the SW Pacific: computer-based reconstructions, model and animations, J. Asian Earth Sci. 20:353–431.

Hayes, D.E., Nissen, S.S. (2005). The South China Sea margins: implications for rifting contrasts, Earth Planet Sci. Lett., 237: 601–616.

Metcalfe, I. (2011). Tectonic framework and phanerozoic evolution of Sundaland, Gondwana Res., 19 (1): 3–21.

How to cite: Guo, D.: Constrained Gravity Inversion for the Moho Depth and Tectonic Patterns in South China Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4845, https://doi.org/10.5194/egusphere-egu24-4845, 2024.

X2.9
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EGU24-7561
Hongtao Hao and Minzhang Hu

Coseismic gravity changes provide significant information for the study of the mechanisms of large earthquakes and for developing fault models (Sun, 2012). In this research,  coseismic gravity changes of the 2008 Ms8.0 Wenchuan earthquake in China were studied by using gravity observation data and simulation based on a fault model.

Firstly, a fine processing of relative and absolute gravity data from the Longmenshan Gravimetric Network was carried out and observed gravity change of 22 stations near this earthquake were obtained; Secondly ,simulation of coseismic gravity changes was conducted based on half-space dislocation theory using the fault model obtained by Wang et al(2008) through inversion with multiple types of geodetic survey data, including GPS, INSAR, and leveling, and the results were compared with the observations..

It was found that the observed and simulated results are basically consistent, showing that the significant changes are mainly concentrated in the near-rupture zone in the hanging wall of the Yingxiu–Beichuan fault and that the changes decrease rapidly away from the rupture zone. The changes exhibit a positive to negative trend from east to west in the footwall of the Yingxiu–Beichuan fault and have a distribution characterized by alternate positive and negative changes in the hanging wall of the fault. This demonstrates the reliability of the observed results and the reasonableness of the fault model used in this paper.

In the near-rupture zone on the west and east sides of the Yingxiu–Beichuan fault, there are still some differences between the observed and simulated results. The trends in the spatial distribution of these differences exhibit a deviation similar to “phase delay”; in other words, an observed result deviates from the corresponding simulated result in terms of spatial position, which is speculated to be caused by errors in the geometric parameters and in the slip distribution of the fault model. After the slip distribution of  the Pengguan fault model was modified based on the actual surface rupture distribution, the simulated result at the Hongjiawan station near the eastern boundary of the fault model showed greater consistency with the observed result. This indicates that the observed gravity change results in this paper can provide an important reference for further detailed study of the fault model.         

            Fig1.Schematic of the Chengdu Gravimetric Network                        Fig2.Spatial distribution of observed gravity changes and simulated results

 

 

How to cite: Hao, H. and Hu, M.: Coseismic gravity changes of the 2008 Wenchuan earthquake in China observed by surface gravimetric data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7561, https://doi.org/10.5194/egusphere-egu24-7561, 2024.

X2.10
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EGU24-14212
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ECS
Magnetic map-making for advanced applications: Quantitative comparison of frequency dependent features, errors, and uncertainties in gridded magnetic data
(withdrawn)
Patrick Duff and Aaron Nielsen
X2.11
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EGU24-8934
Suzanne McEnroe, Madeline Lee, Yuleika Madriz, Richard Gloaguen, Zeudia Pastore, Peter Lelièvre, and Nathan Church

Multiple magnetic surveys, including fixed-wing, helicopter-borne, uncrewed aerial vehicle (UAV), and ground magnetics have been acquired over parts of the Bjerkreim-Sokndal layered intrusion (BKS) in Rogaland, Norway. The Proterozoic 230 km2 Bjerkreim-Sokndal layered complex intrudes into anorthosites and hosts recurrent megacyclic units (MCU) with varying cumulus and critical minerals. Some MCUs are associated with strong magnetic remanence, resulting in Koenignsberger ratios (Q ratio) over 5 and anomalies of 12 000 nT below background.  A comparative analysis of these surveys over the Bjerkreim Lobe provide insights into what features can be mapped at different scales. Here we focus on new geological details provided by UAV, ground, and mineral scale surveys.  A UAV can typically operate at a maximum altitude of 150 m above terrain to a minimum of tens- of centimeters in ideal conditions. Thus, UAV magnetic surveys are optimal for understanding the change of a magnetic anomaly with varying source-separation through multiple flight altitudes. Survey altitudes by UAVs overlap with the source-sensor separation of ground and low-altitude crewed flights, therefore allowing a comparative analysis.

In 2023, the Norwegian University of Science and Technology and Helmholtz Institute Freiberg acquired coincident magnetic survey grids by UAV and ground magnetometer over key sites in the Bjerkreim lobe. Here we compare results of crewed-, uncrewed-, and ground-based data collected over the eastern margin of the Bjerkreim lobe and assess how these impact subsequent geologic interpretations. The petrophysical database for the survey area also contains > 1500 previously collected samples in combination with surface geometry information. This database in combination with the extensive lateral magnetic survey data at various sensor heights and other available complementary geophysics, including gravity, provide excellent parameters and constraints for forward modelling and inversions.

In the Bjerkreim lobe two MCU have significant magnetic remanence where anomalies are several thousand nT below background due to natural remanent magnetizations that are typically > 15 A/m. Therefore, an additional focus is on understanding the nature of the magnetic mineralogy using high-resolution scanning magnetic microscopy. These large amplitude magnetic anomalies may also cause logistical challenges for both airborne- and ground magnetic surveying. UAVs employ onboard magnetometer for navigation and attitude corrections which can be impacted by these large magnetic gradients. Similarly, significant noise or sensor drop-outs when the sensor’s dead zone is aligned with these large, often steep, magnetic gradients.

How to cite: McEnroe, S., Lee, M., Madriz, Y., Gloaguen, R., Pastore, Z., Lelièvre, P., and Church, N.: What can we learn from magnetic surveys at different scales? Geological insight from mineral to airborne surveys in the Bjerkreim-Sokndal Layer Intrusion, Norway, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8934, https://doi.org/10.5194/egusphere-egu24-8934, 2024.

X2.12
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EGU24-17476
Alessandro Fedele, Umberto Riccardi, Tommaso Pivetta, Stefano Carlino, and Giuseppe Ricciardi

High-precision observations of gravity plays a central role in modern approaches for active volcano monitoring. Time-lapse observations over a network of benchmarks are frequently used to detect underground mass redistribution in the plumbing system of active volcanoes. Such approach however does not allow to retrieve small mass variations occurring over short terms (i.e. few hours or days). To fill this gap, continuous gravity monitoring at a fixed station may be employed. In January 2023 the relative gravimeter gPhoneX#116 was installed at the WWF Nature Reserve of Astroni volcano, in the Campi Flegrei caldera, to further complement time-lapse observations periodically performed over a network of benchmarks. During the 1-year of recordings, the gPhone has continuously recorded the relative gravity changes, only shortly interrupted by a few technical issues. The purpose of the observations is to monitor continuously the short-term gravity signals in one of the world's highest-risk volcanoes; to pursue this objective targeted and meticulous corrections need to be applied to remove the effect of several other geophysical effects, such as tides and atmospheric effects, which may superpose on the signals of interest. Special effort was devoted to the study of instrumental drift, which can mask actual gravity changes due to mass variations occurring in the volcanic and geothermal systems. In this contribution we report the various processing steps and analysis performed to obtain reliable parameters of the Earth tides, non-tidal corrections and gravity residuals. The retrieved Earth tide model is then used to properly reduce tidal effects in high-precision relative and absolute gravity measurements.

How to cite: Fedele, A., Riccardi, U., Pivetta, T., Carlino, S., and Ricciardi, G.: A year-long gravity record at Astroni, Campi Flegrei (Southern Italy): some considerations on data processing for volcano monitoring and precise gravity tides, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17476, https://doi.org/10.5194/egusphere-egu24-17476, 2024.

X2.13
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EGU24-15133
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ECS
Marvin Reich, Camille Janvier, and Andreas Güntner

Quantum sensors have gained increased attention in the last years, both from the applied but also from the manufacturer perspective. Most instruments are still limited to operation within a dedicated lab. With the Absolute Quantum Gravimeter (AQG), one device has already proven mobile capabilities and was used in several research studies. This application perspective is an important topic for new instruments, in order to meet scientific requirements in terms of usability and usefulness for various research interests.

One of these research interests is hydrology. From the monitoring perspective, hydrological observations in the field traditionally rely on point measurements, often in form of invasive sensor installations. These spatially-limited observations sometimes complicate natural hydrological process investigations. An advantage is provided when using the hydrogravimetric method, with its integral nature of monitoring water mass changes as a whole.

In this contribution, we address the above-mentioned important topics for a first feasibility study of an emerging instrument: the Differential Quantum Gravimeter (DQG). Developed by Exail Quantum Sensors, the DQG measures the acceleration due to gravity and the vertical gravity gradient simultaneously. It is an industry-grade demonstrator that has been operational for three years now and has achieved state-of-the-art sensitivity on the gradient of about 60E/sqrt(tau) and a long-term stability on the gradient around 1E. For gravity measurements the performances are on par or better than the AQG with a sensitivity of 600nm/s²/sqrt(tau) and a stability down to 5nm/s².

In preparation for first field measurements, we were interested in its performance for resolving hydrological dynamics and processes. We set up different hydrological modeling scenarios to forward model gravity responses and their DQG-related gravity gradients from water mass changes. Scenarios for obtaining these water mass changes consisted of vertical 1D models using the software Hydrus. Developing scenarios from very simple to more complex soil layer setups, we tested different forcing types (precipitation, evapotranspiration) with varying magnitudes and durations. The overall objective was to simulate resulting gravity gradients at different locations as the DQG would monitor them. Varying the theoretical placement of the DQG within the model domain enabled us to investigate its sensitivity to the simulated hydrological processes with respect to its location and distance to different magnitudes of water mass changes. Forward modeled data was averaged at different time periods and combined with realistically expected noise of the instrument. The study helps to evaluate the capabilities of the instrument as a tool to observe water fluxes in the soil, as well as optimal implementation of the DQG for planning first field measurements.

How to cite: Reich, M., Janvier, C., and Güntner, A.: Investigating the feasibility of resolving hydrological processes with a Differential Quantum Gravimeter by hydrological scenario modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15133, https://doi.org/10.5194/egusphere-egu24-15133, 2024.

X2.14
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EGU24-19368
Detecting the magnetic characteristics of submarine volcanic area off the coast of northern Taiwan
(withdrawn after no-show)
Chung-Liang Lo, Shu-Kun Hsu, Shiao-Shan Lin, Ching-Hui Tsai, Song-Chun Chen, and Pin-Ju Su
X2.15
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EGU24-1294
Benjamin Haser, Thomas Andert, and Roger Förstner

Asteroids and moons are promising targets for physical space exploration. The use of physically-based simulations within a virtual environment for (deep) space missions can significantly benefit the testing and validation of guidance, navigation, and control algorithms. This approach offers advantages in terms of cost and time efficiency. Especially for orbit propagation and landing maneuvers, information about the gravitational field is crucial. However, several factors contribute to the complexity of this task, such as limited information available about the inner structure of celestial bodies. The lack of detailed knowledge about their shapes further adds to the challenge.

This study presents a voxel-based mass concentration (MASCON) method to model detailed and realistic density distributions, enabling accurate gravity field determinations. We chose a cube with constant density as first case due to the perfect shape reconstruction and the availability of an analytical solution for its gravity field. To validate our results, we calculated the surface gravity and compared it with the analytical solution, ensuring the accuracy of our calculations. Furthermore, the surface gravity is derived for different resolutions and compared against other state-of-the-art methods like the polyhedral method that provides a closed-form analytical solution of the gravity field for homogeneous density. The other two methods for validation also use a MASCON approach, one utilizing polydisperse sphere packing and another with MASCON represented in spherical coordinates. The relative errors of the gravitational acceleration between the four methods will be evaluated for a cube and sphere, with homogeneous density.

The second aspect of this study was to create a tool that generates realistic density distributions. We are able to successfully reproduce natural environments by placing body-specific restrictions on three-dimensional Perlin noise with additional normalization. The simulator can add the following structural features to the density distribution: an arbitrary number of centralized or decentralized shells, with varying thickness and densities, anomalies of arbitrary size and shape, only restricted by its maximum permille of the body's volume. Furthermore, we implemented different normalization techniques to keep the mass of all generated bodies fixed. Our results show that the tool can generate realistic density distributions and calculate the corresponding gravitational field correctly. The data generated here is used to train Machine Learning and Deep Learning algorithms for gravity inversion.

 

How to cite: Haser, B., Andert, T., and Förstner, R.: Voxel-based Density Models for Accurate Gravitational Field Computation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1294, https://doi.org/10.5194/egusphere-egu24-1294, 2024.

X2.16
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EGU24-18969
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ECS
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Alessandro Ghirotto, Andrea Zunino, Egidio Armadillo, Anna Mittelholz, and Andreas Fichtner

Suitable modelling capabilities paired with planetary-scale datasets provide fundamental information to unravel planets’ interior and evolution. Despite the key role and tremendous effort of decades of scientific missions in advancing the understanding of planets’ subsurface, knowledge about their crustal structures and processes shaping them is still limited. This is mainly due to a sparse record of return samples or meteorites, in addition to the scarcity of surface geophysical measurements. Planets’ crust is however a recorder of ancient geological events leading to nonhomogeneous 3D density distributions, expressed in the form of gravity anomalies. While on Earth combined geophysical data can inform on subsurface properties, for other planets such datasets are sparser, and orbiter-based gravity data is one of few or even the only global-scale source of information related to their interior. Developing an innovative modelling methodology suitable to exploit such orbiter-based data can help infer the 3D density distribution in planets’ crusts, providing key insights to reconstruct their geological history. Here we present GRAVHEDRAL, a fully non-linear 3D inversion methodology of gravity anomaly data suitable for both local- and planetary-scale studies and capable of addressing limitations of existing modelling strategies. Such limitations are related to the challenge of i) characterizing complex 3D density distributions, which are expected in actual geological scenarios, and ii) mitigating the non-uniqueness of the solution. Using GRAVHEDRAL, planets’ interiors (e.g., crust, mantle, etc.) are parameterized in terms of polyhedra with density contrasts expressed as high-order polynomial functions, whose gravity responses can be computed thanks to recently derived analytical formulae. The inversion scheme relies on the Hamiltonian Monte Carlo (HMC) method, a probabilistic approach that is currently gaining momentum in the geophysical community. Compared to other probabilistic approaches, the HMC strategy allows the model space to be explored more efficiently thanks to the gradient calculation of the posterior probability density of the model parameters (i.e., polyhedra node positions and/or density contrasts). Statistical analysis and uncertainty estimation on the model parameters can be performed from the collection of posterior models, enabling the appraisal of different probable geological scenarios to address the non-uniqueness of the solution. GRAVHEDRAL aims to provide the space science community with a flexible tool to help image the still poorly known 3D crustal density distribution of other celestial bodies of our solar system, allowing researchers to test the occurrence of Earth-like geological structures on other terrestrial planets and thus to decipher the reasons behind their different geological evolution.

How to cite: Ghirotto, A., Zunino, A., Armadillo, E., Mittelholz, A., and Fichtner, A.: GRAVHEDRAL: a novel gravity inversion method to unravel planets’ interior, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18969, https://doi.org/10.5194/egusphere-egu24-18969, 2024.

X2.17
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EGU24-16919
|
ECS
Khaoula Charrek, Kristine Walraevens, Thomas Hermans, and Hakim Gabtni

Understanding the communication pathways of deep aquifers in the Tunisian Oriental Atlas along the southern Mediterranean margin, particularly within the coastal Sahel region, is of utmost importance for designing effective well drilling strategies and reducing risks for groundwater drilling.

In this study, we employed Gravity, Time Domain Electromagnetic (TDEM) methods and the variation of the piezometric level to investigate the structural setting and aquifer characteristic. Gravity and TDEM are two geophysical methods that provide insights into the density variation of underground bodies and reveal resistivity distribution at different depths, respectively. By integrating these methods, we aim to unravel the intricate hydrogeological system in the study area.

Our findings highlight a major fault line with a significant water level discrepancy, which is crucial information for groundwater exploration and exploitation. This study provides insights into the hydrogeological dynamics of the coastal Sahel region, facilitating the design of new drilling strategies. The gained knowledge supports informed decision-making in selecting optimal target production zones, ultimately minimizing drilling risks and promoting sustainable groundwater management in the Tunisian Oriental Atlas.

How to cite: Charrek, K., Walraevens, K., Hermans, T., and Gabtni, H.: Unravelling Deep Aquifer Communication in the Coastal Sahel Region: Insights from Geophysical Methods in the Tunisian Oriental Atlas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16919, https://doi.org/10.5194/egusphere-egu24-16919, 2024.

X2.18
|
EGU24-12072
Dmitry Molodtsov, Duygu Kiyan, and Christopher Bean

Regional gravity and magnetic surveys are essential sources of information about the structure and geodynamics of the lithosphere. However, geologically meaningful inversion of gravity and magnetic data usually requires integration with other geophysical methods. We have developed a 3-D joint inversion framework that has the flexibility of using independent inversion codes and model discretizations for each of the included methods, is easily expandable and supports a wide range of the coupling constraints. Here we show its application to the regional geophysical datasets available in Ireland. We present the results of joint inversion of long-period magnetotelluric data, seismic traveltimes, and land gravity – a multiparameter geophysical model of the crust and uppermost mantle of the whole Ireland. On a smaller scale, we present the results of joint inversion of gravity, airborne magnetic and magnetotelluric data for the Limerick Basin, focusing on imaging of a Carboniferous volcanic structure.  The main aim is to better understand the Pb-Zn mineral systems which are controlled by the tectonics of the basement and lower crust. Exploration-scale geophysical surveys and geothermal exploration will also benefit from the regional 3-D geophysical models.

How to cite: Molodtsov, D., Kiyan, D., and Bean, C.: 3D joint inversion of regional magnetotelluric, seismic, gravity and magnetic datasets to image lithospheric structure of Ireland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12072, https://doi.org/10.5194/egusphere-egu24-12072, 2024.

X2.19
|
EGU24-8059
Jörg Ebbing, Jonas Liebsch, and Kenichi Matsuoka

Sub-ice geology significantly influences the dynamics and future evolution of the Antarctic Ice Sheet, but largely inaccessible for direct sampling. Here, we present an approach, where we use a Self-Organizing Map (SOM) to describe sub-glacial properties. Based on attributes derived from gravity, magnetics and radar data from the NASA Operation Ice Bridge dataset in East Antarctica, we train a SOM, where attributes are selected to best represent sub-glacial conditions. Therefore, we study the trade-offs between these data sets helping to identify for which properties these are most sensitive.
The trained SOM identifies the outlines of the main geological structures beneath the ice and supplements models based on inverse and forward modelling. In contrast to such often regional interpretations, the SOM captures small-scale structures at the ice bed, as we illustrate with case examples, and highlights areas with inconsistencies in existing geological interpretations. The SOM can furthermore be used as input for inverse modelling of the physical properties of the sub-glacial geology in Antarctica.

How to cite: Ebbing, J., Liebsch, J., and Matsuoka, K.: Enhancing sub-ice geology in East Antarctica with Self-Organizing maps based on gravity, magnetic and radar data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8059, https://doi.org/10.5194/egusphere-egu24-8059, 2024.