Geoneutrinos, electron antineutrinos produced by the radioactive decay of Uranium (U) and Thorium (Th), offer a unique real-time window into the Earth’s interior composition and radiogenic heat budget. These particles are detected by large-volume underground scintillators where cosmic ray backgrounds are minimized. However, the lack of directional sensitivity in current liquid scintillator detectors, such as Borexino (Gran Sasso massif, Italy), results in a signal degeneracy that necessitates highly accurate models of the local lithosphere to isolate the mantle contribution.
In the framework of the GUESS project (GeoneUtrinos: mESSengers of the Earth's interior), we present a high-resolution 3D geophysical model of Central Italy specifically tailored for geoneutrino signal prediction. Addressing the limitations of previous models, this work adopts a joint multi-disciplinary approach.
The "GUESS model" is computed inverting ground gravity data integrating heterogeneous datasets as prior information in a Bayesian framework. The geological and geophysical prior datasets include: 1D stratigraphic data from deep exploration wells; 2D interpreted seismic profiles and geological cross-sections; 3D passive seismic data (receiver functions) to constrain the Moho discontinuity. This probabilistic framework discretizes the crust into six lithological units, from Quaternary volcanics to the Lower Crust, and explores high-dimensional solution spaces in terms of both geometry and density distribution via simulated annealing. This methodology not only optimizes mass and volume estimates according to both gravity and geophysical data but also provides a quantification of estimation uncertainties by Monte Carlo samples. This workflow demonstrates how the integration of potential field data with seismic and geological constraints provides a robust, geodynamically realistic architecture, advancing both neutrino geoscience and our understanding of complex lithospheric structures.
This study was supported by the project GUESS (GeoneUtrinos: mESSengers of the Earth's interior) funded by European Union – NextGenerationEU, Missione 4, Componente 1(CUP: F53D23001280006).
How to cite: Strati, V., Rossi, L., Albertella, A., Buttinelli, M., Capponi, M., Conti, P., Ermini, A., Maesano, F. E., Maffucci, R., Mantovani, F., Pagano, L., Ramouz, S., Raptis, K. G. C., Reguzzoni, M., Salvini, R., Sampietro, D., Solemani Dinani, P., and Tiberti, M. M.: GUESS: a 3D crustal model of Central Italy for geoneutrino physics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9653, https://doi.org/10.5194/egusphere-egu26-9653, 2026.
The thermal structure of the lower continental crust (LCC) is poorly constrained due to the lack of sufficient data on thermal properties, such as thermal conductivity (TC) and radiogenic heat production (A). However, this is essential for modelling the continental geotherm and heat flow as well as associated temperature-dependent processes and properties. Therefore, the few existing models that calculate the geotherm beneath the upper crustal level simplify the natural variability of TC and A of the lower crust by using averages of only few lithologies or even for an entire crustal section. Notably, individual crustal sections are defined as single thick layers, sometimes tens of km thick, which mismatch the evidence regarding the structure of the LCC. This makes heat flow and temperature calculations prone to errors and may lead to inaccurate and/or biased estimates of absolute values. A recent comprehensive study on the thermal properties of lower crustal lithologies (Lemke et al., 2026), carried out as part of the ICDP-DIVE (Drilling the Ivrea-Verbano zonE) project (Greenwood et al., 2025), fills this data gap and enables us to assess the impact of the variability of thermal properties in the LCC on geothermal and heat flow estimates.
To this end, we set up a 1D steady-state heat flow model of the continental crust, which is divided into an upper crust with constant properties and a lower crust with variable properties. The thermal property structure for the LCC is randomly drawn from lithology-specific A and TCdistributions (Lemke et al., 2026). Similarly, the thicknesses of the individual layers (d) are also drawn from predefined statistical distributions. Based on the available evidence, these distributions are typically Gaussian for the thermal properties (A, TC) and hyperbolic for the layer thicknesses (d), but we also test uniform distributions for these parameters. To assess the influence of the variabilities of TC, A, and d, model types are defined, for which each individual parameter as well as the combined effects of all three parameters are assessed. We compute geotherms upwards and downwards, starting with basal and surface heat flow values, respectively. We test various lower crustal compositions: an intermediate one based on project DIVE as well as mafic and felsic endmembers. By performing numerous realisations for each model setup, the variability, as quantified by two standard deviations of temperature and heat flow is assessed.
The results show that the variability of thermal properties and layer thicknesses has a significant impact on temperature and heat flow. TC variability has the greatest influence on temperature uncertainties, while A variability has the greatest influence on heat flow uncertainties. Thicker layers, and layers with more widely varying thicknesses cause increasing uncertainties. The uncertainties reach ~10% for the heat flow while the temperature uncertainties are comparable to common corrections e.g. related to paleoclimatic signals. The chemical composition of the LCC determines the absolute value of the geotherm, but there is no significant impact on temperature variability. This work thus provides the basis for assessing geotherm and heat flow uncertainties in future models.
How to cite: Lemke, K., Hetényi, G., Luo, Z., Holliger, K., and Schmalholz, S.: Impact of thermal property variability and structural layering in the lower crust on the continental geotherm and heat flow estimates, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17405, https://doi.org/10.5194/egusphere-egu26-17405, 2026.
The 2012 Emilia seismic sequence in the central sector of the Ferrara arc included the 20 May (Mw 6.1) and 29 May 2012 (Mw 6.0) mainshocks, followed by thousands of aftershocks, and ruptured thrust faults belonging to the Ferrara and Mirandola systems buried beneath the Po Plain (Carannante et al., 2015). Several studies have demonstrated the exceptional value of this sequence for crustal imaging: refined aftershock relocations highlighted the activation of adjacent blind thrusts and the structural complexity of the Apennines frontal belt (Govoni et al., 2014), while additional analyses revealed significant lateral heterogeneity along the Ferrara arc (Chiarabba et al., 2014). The dense permanent/temporary network deployed during the crisis produced one of the most complete seismic datasets for northern Italy.
Within this framework, we construct a new three-dimensional a-priori P-wave velocity model for the Emilia–Romagna region, spanning 10–13°E and 44–46°N and parametrised on a 15-km horizontal grid with 3-km vertical spacing. The workflow follows a multi-dataset integration strategy, in which velocity–depth functions are extracted at each node of a horizontal grid and lateral continuity is ensured through spatial smoothing. The model assimilates multiple complementary datasets: Vp control points from the 3-D Po Basin model of Molinari et al. (2015), regional geological cross-sections from the ER3D model (Klin et al., 2019) used as qualitative constraints on basin and thrust geometry, crustal and lithospheric information from published tomographic models (Di Stefano et al., 2011; De Gori et al., 2014) together with the recent adjoint tomography model of the Italian lithosphere (Im25; Magnoni et al., 2022), and structural and seismogenic constraints derived from analyses of the 2012 sequence (Govoni et al., 2014). This multi-source integration produces a geologically coherent three-dimensional starting model that better represents the strong lateral variations of the Po Plain than conventional one-dimensional or poorly constrained three-dimensional initial models.
The resulting model (the a-priori model) is employed as the initial structure for 3-D travel-time tomography, implemented through an iterative inversion approach adapted to the characteristics of the Emilia region. High-quality P- and S-wave arrival times recorded by the seismic network operating during the 2012 sequence offer favourable ray coverage especially in the upper and middle crust. This helps mitigate typical limitations introduced by sharp lateral velocity contrasts and irregular station spacing, improving the reliability and resolution of the final tomographic images.
This work contributes to refine seismic imaging and hazard assessment in the Po Plain. By demonstrating the advantages of constructing a detailed a-priori velocity model in a structurally complex region, it highlights the importance of integrating multiple geophysical datasets to obtain a stable foundation for tomographic inversion. A refined starting model enhances the ability to resolve lateral heterogeneities within the sedimentary basin and better define the geometry of deep thrust systems. The resulting framework supports future investigations of ground-motion amplification, fault interaction and crustal structure along the Apennines front in one of the most industrialised and densely populated regions of northern Italy.
How to cite: Abyat, M., Presti, D., Orecchio, B., Scolaro, S., and Totaro, C.: Crustal imaging of the seismic velocity structure in the Emilia region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-769, https://doi.org/10.5194/egusphere-egu26-769, 2026.
The Mw 7.1 earthquake east of Lake Van on 23 October 2011 triggered intense aftershock activity, with over 10,000 earthquakes recorded between 2011 and 2015. Accurate earthquake locations are essential for reliable seismological studies, and they depend on station coverage, phase-picking quality, and the use of robust velocity models. In this study, waveform data from temporary and permanent seismic networks were combined into a unified dataset. P- and S-wave phases were manually picked, and earthquakes were systematically relocated. A high-quality subset of events was used to derive a one-dimensional (1-D) velocity model, which served as the reference for three-dimensional (3-D) VP and VP/VS inversion. The resulting 3-D velocity models reveal strong lateral and vertical variations along fault zones. Near the mainshock, high- and low-velocity anomalies are observed at multiple depths and extend predominantly in east–west and NE–SW directions. These anomalies reflect the influence of the compressional tectonic regime, complex faulting, and magmatic structures in the region. Our results highlight the value of integrated earthquake relocation and 3-D velocity modeling for understanding seismicity and crustal structure in complex continental collision zones such as Lake Van. Keywords: Earthquake relocation, seismic tomography, inversion, three-dimensional velocity model, seismicity
How to cite: Akkoyunlu, M. F., Kaypak, B., and Oruç, B.: Three-Dimensional Velocity Model Of Lake Van, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21510, https://doi.org/10.5194/egusphere-egu26-21510, 2026.
The convergence of Delhi-Haridwar Ridge (DHR) plays a vital role in understanding the Delhi-Rohtak seismicity and plate segmentation along the Himalaya. The study focuses three segments adjacent to: (i) Indo-Tibetan Suture Zone (ITSZ), (ii) Mohand anticline, (iii) Rohtak in Haryana. Near ITSZ, we have estimated Lithospheric shear-wave velocity (Vs) structure by jointly inverting receiver function, computed using earthquake data from 30 stations of Y2 network, with high-resolution group velocity dispersion data computed using ambient noise and earthquake tomography. A profile along the DHR shows the presence of high velocity material (Vs ~3.6 km/s) at ~38 km depth, with relatively steeper Main Himalayan Thrust (MHT), providing the preliminary impression of the remnants of the ridge. Downwrapping of Moho along the eastern margin of DHR provides insights on the possible segmentation in the region. For Mohand anticline, we recorded seismic ambient noise using a three-component portable seismograph (Tromino) with a natural frequency of 0.1 Hz. We conduct an HVSR (horizontal-to-vertical spectral ratio) study on the recorded data using the Nakamura Method, a technique for estimating the resonance frequency and site amplification caused by different stratigraphic units underlain by the top of the bedrock. Using nine measuring points, variable resonance frequency has been identified in the range of 0.42 to 4.8 Hz, which indicates this region is prone to site amplification as overlain by Doon fan deposits. We further invert the P-velocity (Vp), S-velocity (Vs), and density (ρ) by using Monte Carlo inversion method and identify three different stratigraphic units. The top has a thickness of 3 m with a mean Vs, Vp, and ρ of 218 m/s, 385 m/s, and 1.17 g/cm3, respectively. The second layer has a thickness of 6 m with a mean Vs, Vp, and ρ of 406 m/s, 725 m/s, and 1.7 g/cm3, respectively. The bedrock depth in this region is 127 m with a mean Vs, Vp, and ρ of 582 m/s, 1238 m/s, and 1.8 g/cm3, respectively. Further south in the Rohtak region, we have conducted an active seismic study along five profiles over the DHR with a cumulative length of ~34 km. We have applied the conventional seismic processing techniques to produce the migrated image, in which we observe the presence of structural discontinuities associated with the buried faults. The findings from this study will be essential for seismic hazard assessment and able to explain the seismicity observed in the Delhi-Rohtak region.
How to cite: Anand, A., B. Naik, K., and Ghosal, D.: Delhi-Haridwar Ridge – from Foreland Basin to the Himalayan – an insight through Passive and Active Seismic study, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19424, https://doi.org/10.5194/egusphere-egu26-19424, 2026.
We developed a density model of the lithosphere beneath the Tibet Plateau using the joint inversion of gravity and seismic surface wave data. Based on density and seismic velocity, we revealed the lithospheric thermal structure. Simulation tests show that the lateral resolution of the density model from the joint inversion is 1°, which is higher than that from surface wave inversion. The lithospheric temperature field from the joint inversion of density and seismic velocity shows an uncertainty of ~50°C beneath the Tibetan Plateau, which is much lower than that constrained by seismic velocity alone. Our density and thermal models show that: (1) The lower crust of the Tibetan Plateau has a low density and a high temperature, indicating crustal partial melting and crustal flow. (2) The lithosphere mantle beneath the plateau shows high density and high temperature, indicating partial melting and underplating of the upper mantle. (3) Low-density anomalies appear in the lithospheric mantle of the Bangonghu-Nujiang and Longmucuo-Shuanghu sutures, consistent with low Vs anomalies, possibly caused by the hydration of peridotite in the lithospheric mantle. (4) Low-density and low-temperature anomalies are found in the lithospheric mantle beneath the Yungui Plateau, the Sichuan Basin and the Ordos Block. These anomalies are consistent with the characteristics of cratonic lithospheric mantle.
How to cite: Wan, J. and Luo, Z.: Lithospheric density and thermal structure of the Tibetan Plateau, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17527, https://doi.org/10.5194/egusphere-egu26-17527, 2026.
Joint gravity–seismic inversion is a strong approach for imaging crustal and lithospheric structure, yet its success highly depends on the formulation of the gravimetric direct problem and the quality of input datasets. Here, we investigate how commonly used global and regional grids affect forward gravimetric modelling and the subsequent interpretation of crustal structure in complex tectonic environments.
Following the methodology of Uieda et al. (2017), we construct forward gravimetric models for the Moho depth, based on multiple datasets: SGG-UGM2 gravity measurements, CRUST1.0 crustal thickness models, GlobSed sediment grids, and Gebco bathymetry. We explore the effects of grid resolution, interpolation strategies, and reference model choices on the gravity response, highlighting their influence on the information available to joint inversion schemes.
Previous applications to passive margins provide an example for assessing robustness and sensitivity of the forward-modelling strategy. Extending the approach to a tectonically and magmatically complex region – Azores triple junction – demonstrates how variations in input datasets reveal lateral and vertical heterogeneities. Forward-model experiments indicate which features of the crust are robustly resolvable and how gravity inversion with a seismic constraint can illuminate the nature of the crust, including magmatic additions and crustal thickening.
Our results emphasize that careful selection and treatment of gravity and auxiliary datasets is crucial to maximize geological information from inversions. Explicit consideration of forward-model assumptions, grid effects, and seismic constraints enhances confidence in inferred lithospheric structures, providing a practical framework for integrating multidisciplinary geophysical data in tectonically complex regions.
In addition to regional-scale studies, this methodology can be applied in platform extension projects, providing a cost- and time-efficient preliminary assessment of extensive areas. By highlighting lateral and vertical heterogeneities and identifying zones where gravity responses are most sensitive to subsurface structure, forward-model experiments can guide the prioritization of future data acquisition. Such an approach allows for targeted deployment of more detailed seismic or geophysical surveys, reducing overall exploration effort while maximizing geological insight across large and complex tectonic domains.
How to cite: Gonçalves, S. and Roque, C.: Limitations of gravimetric forward modelling in gravity inversion with seismic constraint: lithospheric studies, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12140, https://doi.org/10.5194/egusphere-egu26-12140, 2026.
The Mackenzie Mountains are an enigmatic mountain range in northwestern Canada. Earthquake focal mechanisms show the mountain range is actively building, even though it is 700 km from the nearest plate boundary, and there is little deformation closer to the plate boundary. In this study, we present new results from the region, including joint local, Pn and teleseismic P tomography, crustal thickness from the Virtual Deep Seismic Sounding method and joint ambient noise/receiver function inversion, and temperatures inferred from earthquake-based and ambient noise-based Rayleigh wave phase velocities. We find a thin lithosphere under the Mackenzies surrounded by a thick lithosphere, suggesting that mantle viscosity variations are contributing to the ongoing deformation. However, we also find only a small increase in crustal thickness in the area which suggests the Mackenzies have not experienced significant contraction, despite several instances of uplift since about 100 Ma. Velocity structure shows a plume-like low velocity structure ascending under the central Mackenzies. The nature of the plume remains a mystery, as it is continuous from the mantle into the crust, but there is no evidence of magmatism at the surface. It may be fluids, magma that hasn’t reached the surface, or a sub-solidus thermal anomaly.
How to cite: Schutt, D., Bankher, A., Sanusi, S., Mousavi, N., Estève, C., Schiffer, C., Fullea, J., and Audet, P.: The Lithosphere of the Mackenzie Mountains in northwest Canada, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3535, https://doi.org/10.5194/egusphere-egu26-3535, 2026.
We present a joint full-waveform inversion (FWI) method that integrates ambient noise, teleseismic, and local earthquake data to image lithospheric structure. Synthetic experiments demonstrate that the joint inversion outperforms inversions using individual data types by leveraging the complementary sensitivities of surface waves, body waves and scattering waves, yielding a more coherent and internally consistent multiparameter lithospheric model that includes compressional-wave velocity (Vp), shear-wave velocity (Vs), and density.
We apply the joint inversion method to investigate the lithospheric structure beneath central California, producing a new three-dimensional shear-wave velocity (Vs) model that reaches a depth of 200 km. Our final model delineates a sharp crustal interface between the Great Valley (GV) and the western Sierra Nevada Batholith (SNB), and clearly images the lithosphere–asthenosphere boundary (LAB) beneath the western coast. These large-scale structural features are in good agreement with recent receiver function and traveltime tomography studies, while our model further resolves small-scale heterogeneities that were poorly constrained in previous single-datatype inversions.
How to cite: Luo, Z. and Wang, K.: Joint Full-Waveform Inversion of Ambient Noise, Teleseismic, and Local Earthquake Data to image the Lithospheric Structure Beneath Central California, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6056, https://doi.org/10.5194/egusphere-egu26-6056, 2026.
The Chhattisgarh Basin in central India is one of the largest Meso-Neoproterozoic intra-cratonic Purana basins. This basin has long been the subject of debate concerning its origin and tectonic evolution. Although its geological and depositional framework are relatively well constrained, the deep crustal architecture and present-day tectonic setting remain less understood. In this study, we employ broadband seismic data from a temporary network of 30 seismic stations deployed across Chhattisgarh Basin and the adjoining Eastern Ghats Mobile Belt (EGMB) to investigate the crustal structure beneath the Chhattisgarh Basin, adjoining Gondwana sediments, the Bastar Craton and the EGMB. Receiver function analysis yields several key observations such as (a) a thin, sharp and nearly flat Moho beneath the Chhattisgarh Basin and Bastar Craton, with an average depth of ~ 37 km and clear multiples, indicating a relatively undisturbed crustal fabric; (b) seismic images beneath the Chhattisgarh Basin do not support models of intra-cratonic rifting or foreland basin development, but instead suggest that sedimentation was possibly due to sea-level fluctuations and the progressive infilling of localized topographic depressions within the Bastar Craton; (c) the Central Indian Shear (CIS) exerts a strong influence on Moho geometry, expressed as a gentle northward dip into the Archean craton segment across the basin–craton boundary, and slightly reduced average shear-wave velocities within the basin; (d) a gradational Moho is detected beneath Gondwana sediments along the north-eastern fringe of the basin; and (e) beneath the EGMB, pronounced Moho offsets of up to ~ 5 km and an eastward dipping gradational Moho delineate significant crustal heterogeneity and bear signatures of an ancient subduction system. These findings provide new constraints on the crustal architecture of the Chhattisgarh Basin and its adjoining tectonic domains, offering valuable insights into the geodynamic processes that shaped central India’s intra-cratonic basins.
How to cite: Maitreyi, M., Singh, A., and Singh, C.: Crustal Structure of the Intra-cratonic Chhattisgarh Basin and the Adjacent Eastern Ghats Mobile Belt, East-Central India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6605, https://doi.org/10.5194/egusphere-egu26-6605, 2026.
The thick Deccan Traps in the Saurashtra Peninsula pose significant challenges for sub-basaltic sediment imaging using conventional seismic methods. To offer a reliable alternative, we employed a transdimensional Bayesian joint inversion of teleseismic P-wave polarizations and receiver functions. Using Bayesian inversion, which offers greater flexibility in incorporating data variance into the objective function due to its probabilistic framework, we obtain 1-D velocity models beneath five broadband stations. The resulting 1-D shear-wave velocity models indicate sub-basaltic sediment thicknesses of ~1.3 km at KHER, 1.6 km at MANK, and 1.4 km at TANA, overlain by high-velocity shear-wave layers (Vs ~2.8–3.0 km/s) with thicknesses of ~0.7–0.9 km. In contrast, no evidence of sub-basaltic sediments was observed at SONT and MORK. The exceptionally low near-surface Vs (~0.85 km/s) and the gradual increase in Vs at SONT suggest the presence of unconsolidated thick sediments (~2.3 km) overlying high-velocity basement rocks (Vs ~3.4 km/s), likely corresponding to exposed Mesozoic formations with no indication of basaltic traps. Meanwhile, MORK exhibits relatively higher near-surface Vs (~2.2 km/s), indicating more compacted sediments with a thinner sediment layer (~0.8 km) overlying ~1.4 km thick volcanic rocks (Vs ~3.1 km/s). This study highlights the potential of passive seismic exploration in imaging sedimentary formations hidden beneath thick volcanic rock layers, offering a cost-effective alternative to conventional geophysical methods.
How to cite: Rajina, A. M. and Maurya, S.: Sub-Basaltic Sediment Imaging with Teleseismic Earthquakes using a Transdimensional Bayesian Approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21032, https://doi.org/10.5194/egusphere-egu26-21032, 2026.
The Northeast India is a tectonically active region situated at the complex junction of the Indian, Eurasian, and Burmese plates. This area, encompassing the eastern Himalayas, the Indo-Burmese Ranges, the Shillong Plateau, the Assam Valley and Bengal Basin, exhibits a highly heterogeneous crustal structure and composition resulting from the continental collision and ongoing subduction of the Indian plate. The objective of this study is to present the first 3D crustal density model for northeast India, obtained through a novel tesseroid-based gravity inversion that accounts for the curvature of the Earth and utilises a Gauss-Newton optimization scheme. This framework is initialised and constrained by a local seismic tomography-based 3D reference density model. The inversion employs a tesseroid mesh parameterisation, in which each density contrast of the tesseroid is solved to minimise a composite objective function that balances data misfit, depth-weighted regularization, and 3D smoothness relative to the seismic reference model. The inversion utilizes the filtered residual gravity anomaly, derived by systematically removing the upper-mantle gravitational effects from the observed Bouguer anomaly and isolating the crustal signal using third-order regional-residual separation, enabling stable recovery of short-wavelength density contrasts.
The resulting 3D crustal density structure reveals: (i) High-density material within the upper crust (~10 km) and the lower crust of the Shillong Plateau indicates the presence of basic intrusions, while the uplifted structural configuration suggests a rigid Archean-Proterozoic basement of the Shillong Plateau exhumed through pop-up tectonics. (ii) Thickened, low-density crust beneath the Eastern Himalaya and Indo-Burmese Ranges reflects ongoing Indian-plate underthrusting and subduction, supported by density gradients that dip north to ~25°N and east to ~93°E, imaging the progressive burial of the Indian crust beneath the Eastern Himalayan arc and Indo-Burmese Ranges, respectively. (iii) Pronounced low-density zones beneath the Indo-Burmese Ranges, indicative of crustal weakening and hydrated fabrics. (iv) Adjacent low-density anomalies within the upper crust of the Assam Valley and the Bengal Basin clearly image the sedimentary fill, while high density at ~25 km depth beneath the Bengal Basin is associated with the presence of oceanic crust (or continental to oceanic transition). These contrasting signatures collectively highlight strong vertical and lateral density variations across the region.
These first-order results provide new quantitative constraints on the crustal density characteristics of major tectonic features in Northeast India, significantly contributing to the understanding of the regional stress field and geodynamic setting of this seismically active region.
How to cite: Pathak, P., Ebbing, J., Haas, P., and Mohanty, W. K.: 3D Crustal Density Distribution of Northeast India from Seismically-Constrained Gravity Inversion, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-421, https://doi.org/10.5194/egusphere-egu26-421, 2026.
The eastern Ladakh region, forming a key segment of the Trans-Himalaya, preserves the tectonic archive of the India–Eurasia collision that led to the closure of the Tethys Ocean, subduction of the Indian lithosphere, and subsequent growth of the Himalayan orogen. Despite its tectonic relevance and geothermal potential, the crustal geophysical framework of this region has remained poorly constrained. To fill this gap, we conducted detailed magnetotelluric (MT) investigations along two strategically positioned profiles: Ukdungle–Hanle–Koyul and the Tso Moriri–Pangong corridor, covering the major suture zones and associated lithotectonic units. Results from the Ukdungle–Hanle–Koyul profile delineate a steeply dipping Indus Suture Zone (ISZ), an 8–10 km thick Ladakh batholith, and a prominent ~6 km-wide conductive body at ~4 km depth beneath the Tso Moriri Crystalline (TMC) complex, with an upward extension along the ISZ. Three-dimensional modelling further reveals that these shallow conductors merge downward into a laterally extensive deep conductive zone interpreted as partial melt underlying southern Tibet and extending into eastern Ladakh. The second MT profile from the TMC complex toward the Pangong metamorphics highlights additional crustal transitions, including the shift from highly resistive Indian crust to moderately resistive crust across the ISZ, the deeper root of the Ladakh batholith at ~18–20 km, and a major 20–25 km deep conductor beneath the Shyok Suture Zone (SSZ), interpreted as a fossil magma chamber. A systematic geoelectric-strike rotation from NW–SE to E–W northward reflects the transition from Himalayan tectonics to the plateau-dominated regime of western Tibet. Together, the profiles also indicate an eastward thinning of the Ladakh batholith, refining the regional crustal architecture.
Keywords: Trans Himalaya, Tso Moriri Crystalline (TMC), Pangong metamorphics, Ladakh Batholith
How to cite: Barman, A., Gayatri, P., Manglik, A., Molli, D. B., Kandregula, R. S., and Narasimha, C. N.: Geoelectric Architecture of Eastern Ladakh: New Insights from Magnetotelluric Imaging Across the Trans-Himalayan Suture System, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-829, https://doi.org/10.5194/egusphere-egu26-829, 2026.
The 1975 Ms 7.3 Haicheng earthquake in the Liaodong Peninsula is well-known worldwide to be the first successful short-term earthquake prediction. To understand the physical basis why this earthquake can be predicted and to elucidate the detailed seismogenic structure of the Haicheng earthquake, in this study we incorporate the variation of information constraints (VI) into body-wave travel-time tomography to determine high-resolution Vp, Vs and Vp/Vs models around mainshock and aftershocks. Compared to previous tomographic methods, the VI-based method can enhance the intrinsic correlation between Vp and Vp/Vs models, thus better resolving regional geological processes and lithological compositions.
We assembled seismic arrival times recorded by permanent and temporary seismic stations in the region. Our results reveal pronounced low-velocity and high Vp/Vs anomalies in the middle to lower crust beneath the seismogenic fault, indicating a mechanically weakened zone likely associated with fluids. Seismic velocities along the fault plane further show that the mainshock nucleated within a transitional zone between brittle, competent granitic rocks featured by low Vp/Vs values and adjacent fluid-rich domains associated with high Vp/Vs values. The spatial distribution of aftershocks along the seismogenic fault shows a strong correlation with zones of high Vp/Vs anomalies. We propose that deep-sourced fluids, most likely originating from the upper mantle upwelling, migrated upward along pre-existing lithospheric-scale fault systems. This progressive fluid infiltration reduced the effective normal stress and mechanically weakened the fault zone. Under sustained tectonic loading, stress became locally concentrated on the strong blocks in the fault plane until fluid overpressure acted as an efficient trigger for rupture initiation. Before the mainshock, the infiltration of fluids can induce intensive foreshocks, which were used as precursors for the prediction of the Haicheng earthquake.
This study highlights the coupled effects of stress evolution, fluid migration, and fault structure in controlling intraplate earthquake occurrence, providing new insights into the physical mechanisms governing seismic hazard in continental interiors.
How to cite: Hao, J., Zhang, H., Huang, Y., Wang, L., and Moorkamp, M.: Fluids Involved in the Occurrence of the 1975 Ms 7.3 Haicheng Earthquake Evidenced From Seismic Velocity Anomalies, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15602, https://doi.org/10.5194/egusphere-egu26-15602, 2026.
The Changbaishan volcanic field (CVF), situated in the southeastern Central Asian Orogenic Belt, hosts a Cenozoic volcanic group including Changbaishan, Longgang, and Jingpohu volcanoes which exhibit distinct activities and surface rock compositions. To understand factors controlling their different behaviors, it is important to conduct integrated analysis of lithospheric thermal, compositional, and rheological structures. Here, we employ a probabilistic joint inversion incorporating surface heat flow, topography, geoid heights and Rayleigh wave phase and group velocity dispersion data to construct the thermal, compositional, and rheological structures of the lithosphere beneath the CVF. Joint inversion results indicate that lithospheric thickness beneath Changbaishan and Longgang volcanoes (~55 km) is significantly thinner than that beneath Jingpohu volcano (~85 km). In addition, a pronounced ~200 km wide asthenospheric thermal anomaly exists beneath the Changbaishan volcano, while it is absent beneath Longgang and Jingpohu volcanoes. Crustal compositions beneath the Changbaishan volcano are dominated by felsic rocks, while they are restricted to the lower crust beneath Jingpohu. Rheological weakening (viscosity <10²¹ Pa·s) extends from the crust to the upper mantle beneath the Changbaishan volcano, whereas the Jingpohu volcano exhibits weak zones only in the lower crust. We propose that the Changbaishan volcano retains a multilevel magmatic system linking the asthenosphere to the shallow crust, sustaining its high activity and diverse eruptive rocks. In contrast, Longgang and Jingpohu volcanoes lack sustained mantle-crust connectivity, resulting in low activity and predominantly alkali basalt eruptions.
How to cite: Zhou, W. and Zhang, H.: Thermal, compositional, and rheological structures of the lithosphere beneath the Changbaishan volcanic field and their controls on volcanic activity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15689, https://doi.org/10.5194/egusphere-egu26-15689, 2026.
Gangwon Province exhibits strong topographic relief and significant variations in Moho depth, necessitating the use of a 3D reference model for reliable crustal velocity imaging. To construct this model, we incorporated ETOPO1 topography, Moho depth estimates from receiver functions, and near-surface sedimentary layers constrained by P-wave polarization angle inversion essential for improved fitting of short-period dispersion curves. Rayleigh-wave phase and group velocities were measured from ambient-noise cross-correlation functions using data from 101 broadband seismometers and accelerometers for periods of 1–16 s. To extend sensitivity to deeper structures, we also included longer-period (10–40 s) Rayleigh-wave phase velocities derived from regional Helmholtz tomography. These three complementary datasets were jointly inverted to produce a high-resolution 3D S-wave crustal velocity model of Gangwon Province. The resulting model reveals pronounced low-velocity anomalies bounded by the Inje and Geumwang faults, suggesting the presence of compositional heterogeneity and mechanically weak zones. These results provide quantitative 3D constraints on major fault systems and crust–uppermost mantle structure in Gangwon Province.
How to cite: Kim, M., Chang, S.-J., Sohn, Y. J., and Kim, K.-H.: Joint Inversion of Rayleigh-Wave Phase/Group Velocities Using a 3D Reference Model for Crustal Velocity Structure of Gangwon Province in the Korean Peninsula, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4724, https://doi.org/10.5194/egusphere-egu26-4724, 2026.
Receiver functions derived from teleseismic events are sensitive to subsurface structural effects beneath a seismic station and are therefore useful for estimating crustal thickness. More than 300 seismometers have been installed on the Korean Peninsula since the 2016 Gyeongju earthquake (ML 5.8), the largest instrumentally recorded earthquake in the region. This monitoring environment is suitable for obtaining high-resolution estimates of Moho depth and Vp/Vs ratios, considering the spatial resolution of receiver function analysis. Receiver functions were computed from 2,361 teleseismic events (Mw 5.5–7.0; epicentral distances of 30°–90°) recorded between January 2003 and January 2024. Azimuthal corrections were applied to the receiver functions by searching for the direction that minimizes energy on the transverse component. For specific stations, temporal variations in the azimuth angle were observed. Consequently, a moving-average technique was applied, and only periods with stable azimuth angles were used for the analysis. Subsequently, the Moho depth and Vp/Vs ratio were determined at the location of the maximum stacking amplitude in the H–κ domain. For stations exhibiting double peaks in the H–κ domain, normalized receiver functions were clustered based on the sum of Euclidean distances, and the H–κ analysis was repeated. The derived Moho depths indicate that crustal thickness is thinnest (~30 km) beneath the Gyeonggi Massif and thickest (~34 km) beneath the Yeongnam Massif. In the eastern Korean Peninsula, the observed crustal thickness is inconsistent with isostatic equilibrium, suggesting the influence of dynamic-topography-related downwelling. A Moho depth exceeding 34 km is also observed in the southwestern Okcheon Belt. The Gyeonggi Massif shows the lowest Vp/Vs ratio (1.72), whereas higher values (>1.78) occur in the eastern Gyeongsang Basin and the northeastern Gyeonggi Massif. High Vp/Vs ratios are interpreted to be related to the emplacement of Cretaceous Bulguksa granites.
How to cite: Lee, D. and Kim, S.: Estimation of the high-resolution Moho discontinuity beneath the Korean peninsula by receiver function analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6423, https://doi.org/10.5194/egusphere-egu26-6423, 2026.
The Alps is a complex and dynamic region and although it has been extensively studied and has provided crucial information in understanding orogenic processes, there is still much that is continually debated in this region, such as the interactions and variations between crustal and mantle processes and structures. The AlpArray seismic network was deployed with the intention of providing a dataset that could help resolve some of these debates. It is made up of 628 stations (352 permanent and 276 temporary) deployed across 11 countries covering the greater Alpine region. The density and spatial consistency of this network provides a unique opportunity to examine the seismicity in the Alps as well as to apply geophysical methods such as tomography to provide high resolution images of this area allowing for a better understanding of these crustal and mantle dynamics. Previous studies have used this rich dataset to implement these methods such as local earthquake tomography, ambient noise tomography and teleseismic tomography. However, none have jointly inverted local and teleseismic datasets with gravity, which is what we undertake with this research. We are in the process of creating an augmented catalogue of P and S wave arrivals using an automated algorithm called REST which has already been successfully used in another orogenic region, the Andes. This catalogue will be used in the joint inversion with previously compiled teleseismic and gravity datasets to give a comprehensive image of the subsurface structure down to mantle depths consistent with these 3 datasets.
How to cite: Maharaj, A., Hetényi, G., and Roecker, S.: High Resolution Joint Inversion of the Greater Alpine Region using the AlpArray Seismic and Gravity Datasets, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10874, https://doi.org/10.5194/egusphere-egu26-10874, 2026.
The Carpathian–Pannonian Region (CPR) is one of the most seismically active areas in Central Europe, as evidenced by destructive events such as the Mw 7.7 Vrancea earthquake of 1940. Understanding the crustal structure beneath the CPR is essential for understanding earthquake processes, improving high-resolution earthquake location, and mitigating seismic hazard. In this study, we present a 3-D S-wave velocity model of the CPR obtained by jointly inverting group and phase velocity dispersion data using a trans-dimensional Bayesian approach. This method provides a more robust, well-resolved crustal and uppermost-mantle structure than previous studies relying solely on group-velocity inversion. Our results show low velocities at 5–10 km depth beneath the Pannonian Basin, and elevated velocities at ~30 km depth beneath the Great Hungarian Plain, while surrounding mountain regions exhibit relatively low velocities at ~40 km depth. Velocities become nearly uniform by a depth of 50 km. Cross-sections reveal a pronounced upper-crustal low-velocity zone beneath the basin and a mid-crustal low-velocity layer at ~20 km depth along the Tisza–Dacia profile, producing a layered geometry resembling the “crocodile” pattern reported in other tectonically complex regions. Importantly, the Moho is expressed at different S-wave velocity levels across the CPR: the 3.8 km/s isoline is close to the Moho beneath the basin, whereas the 4.2 km/s isoline better represents the deeper Moho beneath the surrounding mountains reported by previous studies (Thapa & Vlahovic, 2025). Identifying the Moho using region-appropriate Vs iso-velocity values highlights how variations in crustal composition and thermal structure influence the Moho’s seismic velocity signature. Our study provides a refined crustal framework of the CPR, providing critical constraints for understanding its tectonic evolution and improving regional seismic hazard assessment.
How to cite: Thapa, H. R., Vlahovic, G., Subedi, S., and Adhikari, L. B.: Crustal Structure Beneath the Carpathian–Pannonian Region Using Ambient Noise Tomography, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1378, https://doi.org/10.5194/egusphere-egu26-1378, 2026.
Southern Italy is a tectonically active region presenting a high seismic risk. The convergence between the African and European plates has produced intense crustal deformation, widespread active faulting zones, and a highly complex tectonic architecture. Developing 3-D seismic tomography models in such a setting is essential for improving our understanding of the crustal heterogeneity and its impact on seismic hazard. Here we measure the dispersion properties of cross-correlation functions obtained from ambient noise interferometry for 69 broadband stations for the period between 2020 to 2024. To improve the azimuthal coverage and address data gaps, we extract group velocities of surface waves from 28 regional earthquakes (M>5). We jointly invert the earthquake and ambient noise dispersion data to obtain Rayleigh and Love wave group velocity maps at periods ranging from 5 to 23 s in a probabilistic framework. We then perform 1-D depth inversions of both surface wave types to retrieve depth-dependent isotropic Voigt velocity (VVoigt) and radial anisotropy models. The resulting surface-wave group velocity distributions, together with the 3D VVoigt and shear-wave radial anisotropy models, reveal pronounced seismic signatures associated with the Lagonegro Basin unit, located between the Apennine chain and the Apulian carbonate platforms. These findings provide new constraints on the crustal structure of Southern Italy and contribute to a more refined understanding of its tectonic and seismic behavior.
How to cite: Muzellec, T., Estève, C., Kramer, R., and Bokelmann, G.: S-wave velocity and radial anisotropy structure of the Southern Italy from probabilistic tomography inversion, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2362, https://doi.org/10.5194/egusphere-egu26-2362, 2026.
Serpentinisation is a water–rock reaction in ultramafic lithologies that can generate natural hydrogen and strongly modifies rock density and magnetic susceptibility. Quantifying the spatial distribution of serpentinized bodies is therefore essential for assessing the subsurface potential of natural hydrogen systems.
The Münchberg Massif (northern Bavaria, Germany) is an exhumed stack of tectonic nappes of different metamorphic grades that hosts several outcropping serpentinite bodies. This provides a rare opportunity to study serpentinisation in a setting that is typically buried at considerable crustal depths. The serpentinites are mainly exposed in the southern and southeastern part of the massif and coincide with pronounced, high-amplitude magnetic anomalies attributed to elevated magnetite contents. Despite detailed petrological and geochemical studies, the structural continuation of these bodies toward the north and northwest beneath overlying nappes remains poorly constrained.
We address this problem through joint inversion of gravity and magnetic data, exploiting the characteristic properties of reduced bulk density and elevated magnetic susceptibility in serpentinized ultramafic rocks relative to the surrounding crystalline basement. We integrate newly acquired high-resolution airborne gravity and magnetic observations with vintage seismic reflection constraints and site-specific petrophysical measurements (density and magnetic susceptibility) conducted on samples collected from surface outcrops. We used topography-aware forward modelling and wavelet compression to efficiently handle dense airborne datasets. Geological and petrophysical information is incorporated through bound/interval constraints, while seismic reflectors provide structural guidance to steer the inversion toward geologically plausible geometries and reduce non-uniqueness.
Preliminary joint inversion results of serpentinites reproduce the observed magnetic anomaly patterns consistent with outcrop-based measurements. First joint gravity–magnetic models indicate that combining density and susceptibility constraints with structural guidance from vintage seismic reflection data improves the robustness of inferred serpentinite geometries compared to magnetic-only inversions, particularly with respect to thickness distribution and subsurface continuity beneath the massif.
The Münchberg Massif thus serves as a natural test site for developing and validating geophysical workflows to characterize potential natural hydrogen systems in settings where serpentinites are concealed beneath crystalline or sedimentary cover.
How to cite: Klitzke, P., Sobh, M., Ruppel, A., Bagge, M., Koglin, N., Hasch, M., Christiansen, R., Fazlikhani, H., Goldmann, J.-F., Heyde, I., and Löwer, A.: Imaging of Serpentinites beneath the Münchberg Massif (Germany) using Joint Gravity and Magnetic Inversion, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19008, https://doi.org/10.5194/egusphere-egu26-19008, 2026.
Posters virtual: Tue, 5 May, 14:00–18:00 | vPoster spot 1b
EGU26-10972 | ECS | Posters virtual | VPS24
Crustal Seismic anisotropy in Sikkim Himalaya: Implications for deformationTue, 05 May, 14:18–14:21 (CEST) vPoster spot 1b
Collision and relentless underthrusting of India beneath Eurasia resulted in large-scale deformation of the Indian lithosphere. Anisotropic parameters serve as a good proxies to decipher deformation in such complex orogenic collision zones. In this study, we present anisotropy characteristics of the crust beneath Sikkim Himalaya using harmonic decomposition of P-to-S converted phases identified in P-wave receiver functions (P-RFs). Analysis of azimuthal variation of these phases enabled parameterizing the crustal anisotropic properties, with depth. Initially, 11,087 high quality P-RFs were computed using waveforms of teleseismic earthquakes having magnitude ≥ 5.5 and signal to noise ratio ≥ 2.5 within an epicentral distance range of 30° - 100°, recorded at a network of 38 seismic stations deployed in Sikkim Himalaya and the adjoining foreland basin. Analysis of the first three harmonic degrees (i.e. k= 0, 1 and 2) reveals that the upper crustal anisotropy is oriented WSW-ENE to E-W, coinciding well with the trends of crustal microcracks and fractures. The mid to lower crustal anisotropy aligns predominantly with the dipping decollement layer along which the Indian plate is underthrusting Tibet. An orthogonal reorientation is observed within the extent of the Dhubri-Chungthang Fault Zone authenticating its role in segmenting the orogen. The lower crustal anisotropy is highly perturbed signifying a highly heterogeneous nature of the Moho. Existence of multiple layers of anisotropy possessing distinct geometries varying with depth could be an indication of a highly complex deformational regime resulting from active crustal shortening.
How to cite: Kumar, G., Singh, A., Singh, C., Saikia, D., and Kumar, M. R.: Crustal Seismic anisotropy in Sikkim Himalaya: Implications for deformation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10972, https://doi.org/10.5194/egusphere-egu26-10972, 2026.
