Abstract Coal-rock structures in deep coal-bearing strata, due to their intricate mechanical properties, are the primary carriers of rock burst hazards. This study, incorporating singular point catastrophe theory, develops a mathematical model of the coal-rock to investigate the instability mechanisms and influencing factors of these structures. The results reveal the following: (1) By integrating the sharp corner mutation model, the mathematical formulation of the failure criterion for the coal-rock composite system was derived. (2) The failure process of the coal-rock composite structure is gradual. The strength of the coal significantly influences the peak instability strength of the composite structure, whereas the strength of the rock has a relatively minor impact on it. (3) As the proportion of rock thickness decreases, the number of fractures within the rock also diminishes, with these fractures primarily developing on the side of the rock adjacent to the coal-rock contact surface. The findings of this research can serve as valuable references for the prevention of rockbursts in the protection of coal pillars.

Abstract A three-dimensional (3D) geologic framework has been developed for the conterminous United States (U.S.) as part of the U.S. Geological Survey National Crustal Model to enhance seismic hazard modeling. The geologic framework is created from geologic maps and multiple subsurface geologic unit boundaries including the base of the Miocene, Cenozoic, Phanerozoic, and the Mohorovičić discontinuity. Modifications are made to surficial geologic maps to remove discontinuities across state and country borders. The subsurface distribution of rock type and age is extrapolated from the surface, seeded with subsurface geologic information, and constrained by a map of basement geology. The framework provides the basis for estimates of subsurface seismic velocity and density that is needed to improve estimates of earthquake ground shaking and seismic hazard. The present framework greatly expands and updates a previously published 3D geologic framework of the western part of the U.S. that was itself a first-of-its-kind digital 3D portrayal of the nation.

Abstract Computing seismic traveltime constitutes an essential task for seismic imaging and inversion processes. Accurate traveltime computation provides essential parameters for simulating seismic wave propagation, locating seismic sources, establishing velocity models, and seismic imaging. Therefore, a method for calculating seismic traveltime that is accurate, efficient, and stable holds significant research and practical value. The Multi-Stencils Fast Marching (MSFM) method improves upon the Fast Marching Method by employing multiple stencils to enhance accuracy, addressing the issue of significant errors in diagonal directions. However, its computational complexity increases exponentially with the number of stencils, leading to efficiency bottlenecks in large-scale models. This study proposes an enhanced MSFM method incorporating coarse-grid interpolation to compute seismic traveltime in complex velocity models. The technique extends the conventional MSFM framework by refining its narrowband expansion mechanism, utilizing coarse-grid technology to interpolate values from coarse-grid nodes to fine-grid nodes, thereby improving computational efficiency and reducing memory usage. The improved MSFM algorithm is validated using multiple models, demonstrating that it significantly enhances computational efficiency while maintaining good accuracy.

Abstract Accurately estimating the thickness of Arctic multiyear sea ice is essential for understanding cryospheric dynamics and monitoring climate change. Ground-penetrating radar (GPR) is widely used in terrestrial geophysical applications, including subsurface imaging for geological mapping, permafrost investigations, and structural assessments of the lithosphere. In recent years, GPR has also been applied to sea ice studies, particularly for detecting the snow-ice and ice-seawater boundaries. However, accurately resolving the ice-seawater boundary remains challenging due to the presence of a transition zone, where brine drainage causes gradual changes in dielectric properties. This leads to significant signal attenuation and reflection ambiguities in GPR data. To improve GPR interpretation under such conditions, this study applies attribute analysis techniques specifically instantaneous amplitude, instantaneous phase, and instantaneous Q-factor. These attributes enhance the interpretability of GPR signals and assist in identifying boundaries within brine-affected transition zones. In addition, field data acquired from GPR systems were used to evaluate how attribute analysis contributes to the interpretation of sea ice structure, demonstrating the practical value of these attributes for delineating internal boundaries and transitions within multiyear sea ice. Comparison with direct ice thickness measurements and electromagnetic (EM) surveys conducted along the same transects was used to assess the performance of the attribute-based interpretation. The attribute-based interpretation provided supplementary information that improved the interpreter’s ability to resolve complex boundary conditions. Compared to traditional methods relying on empirical calibration or multi-frequency analysis, this approach offers improved support for ice thickness estimation in challenging sea ice environments.

Abstract River-network reorganization is a key process to maintain drainage connectivity in tectonically active mountain ranges. The southern Himalayan front has experienced several drainage diversion events that changed river courses in the hanging wall of the orogenic wedge and controlled growth of mega fans to the south. In this study, we dated Late Pleistocene sediments of the paleo-Sutlej River in the western Himalaya to reconstruct the last river-drainage development prior to the sediment uplift. Late Quaternary faulting along the Himalayan Frontal Thrust (HFT) and associated back-thrusting has uplifted the paleo-Sutlej sediments and preserved them as a low-relief surface on top of the Janauri frontal anticline. New luminescence (n = 11) and paired cosmogenic nuclides (10Be and 26Al) (n = 10) chronologies combined with field mapping and geomorphic analyzes constrain rapid changes of the paleo-Sutlej River. We date widespread Late Pleistocene sediment deposits from ~47 to 30 ky on the presently elevated anticline and in the infilling of a piggyback basin. Cosmogenic burial signals from fan sediments exceed ~0.5 My and suggest transient sediment storage after erosion in the source region and before deposition at the sampled location. The growing anticlinal structure was traversed by a Paleo-Sutlej channel until 26.5 ± 3.5 ky dated by an abandoned fan surface. We are able to constrain the minimum mean uplift rate to 6.5 ± 2 mm/y at the overlapping fault segment boundaries of the anticline. We also identified a second younger erosional surface on top of the anticline (14.8 ± 2.2 ky) that we relate to drainage reorganization due to tilting of the anticline surface during uplift. We propose that a combination of climatically induced sediment transport capability changes combined with tectonic uplift at the HFT is responsible for the course changes of the Sutlej River.

Abstract Understanding geological controls on subsurface fluid flow is critical for groundwater resource management and aquifer protection and is particularly challenging in faulted carbonate aquifers due to dissolution and conduit development. We conducted an integrated hydrologic study of the Hidden Valley fault zone in mechanically layered Glen Rose Formation (Trinity Aquifer) exposed in the Canyon Lake gorge in central Texas. Initial hydrologic assessment included geochemistry of water from springs, water wells, and adjacent Canyon Lake, and water temperature, conductivity, and flow monitoring. Geochemistry results indicate spring sourcing from Canyon Lake rather than the Trinity Aquifer. Water temperature and conductivity monitoring indicated complex water movement in the fault zone including spring discharge, surface flow, water infiltration (recharge) along the fault zone, and subsurface flow via secondary porosity (e.g. faults, fractures, vugs). We conducted tracer tests with three distinct dyes (Uranine, Eosin, Phloxine B) at three locations in the fault zone and monitored water at (i) down-gradient springs within the fault zone, (ii) wells in the hanging wall and footwall of the Hidden Valley fault zone, and (iii) the Guadalupe River upstream and downstream of confluence with the gorge outflow. One or more dyes were detected at all down-gradient spring, seep, and stream monitoring sites, but none were detected at monitored water wells or upstream river sites. Uranine injected into a recharge feature (sink) along the fault core travelled laterally underground along the fault zone up to 1993 m/d. Eosin injected in the footwall travelled across the footwall fault damage zone (approximately perpendicular to the fault) at 987 m/d and parallel to the fault at up to 2596 m/d. Fault zone deformation features, including normal faults, extension fractures, and associated dissolution, produced strongly anisotropic hydraulic conductivity that is >7 times larger parallel to the fault compared with perpendicular to the fault.

Abstract The West Bohemia region in Czechia is well known for its frequent seismic activity, particularly earthquake swarms with magnitudes up to 3–4. Seismicity has been documented since the sixteenth century, with pronounced activity since 1985. Earthquakes concentrate in the Nový Kostel area where hypocenters align along a N–S trending fault zone over 15 km long and at depths of 6–13 km. Despite this activity, a clear surface trace of the responsible fault has remained elusive. This study reports the discovery and investigation of a surface manifestation of the Čirá–Kopanina fault (ČKF), which aligns with the Nový Kostel focal zone (NKFZ). A multidisciplinary approach, integrating geomorphological, geophysical, and seismological analyses, was used to explore the ČKF trace and its near-surface structure. Aligned geomorphological features, including a NNW-trending scarp and linear springs and wet areas, suggest a fault trace extending southward from Čirá village. A combined geophysical survey, including electrical resistivity tomography (ERT), shallow seismic refraction, gravity survey, and electromagnetic induction, confirmed the presence and characteristics of the fault. ERT data revealed a continuous zone, up to 200 m wide, of low resistivity interpreted as fractured, weathered, water-saturated rocks, indicating multiple parallel fault strands. Measurements across the prominent scarp at Čirá village consistently confirmed the fault zone’s presence with all applied methods. Relocation of earthquake hypocenters (1991–2022) showed a narrow, steeply dipping fault zone striking 169° and descending from 6 to 13 km depth. Subparallel and oblique segments dipping west support the interpretation that the ČKF trace represents the surface expression of the NKFZ. The fault scarp implies past surface-rupturing earthquakes, and both historical ruptures and present-day swarms with magnitudes up to ML 5 likely occur within the same fault system. These findings emphasize the ČKF’s recent tectonic activity and its role in regional seismic hazard assessment.

Abstract This study presents a parameter optimization strategy for generating synthetic seismic data that closely match the characteristics of target field data, aiming to improve deep learning-based fault detection. An analysis in the latent space is conducted to assess the similarities between synthetic data and target field data. Based on the results from this analysis, we optimize the parameters for generating synthetic data. Further refinement of the data generation process is achieved through the application of Explainable Artificial Intelligence (XAI). The fault interpretation results using the U-Net model trained on optimized synthetic data show significant improvements compared to those from the model trained on unoptimized data. The optimization strategy employed allows for the visualization of feature distributions in the latent space, offering a direct understanding of how the distribution of features shifts depending on the desired parameters. This approach not only circumvents the limitations associated with using field data for training, such as the challenge of acquiring accurate fault structure labels and the scarcity of sufficient training data, but also overcomes the potential discrepancies in interpretation results due to significant deviations in the characteristics of synthetic data from the target field data. The proposed optimization framework improves the performance of deep learning models in fault interpretation and establishes an advanced approach for using synthetic data in deep learning–based seismic interpretation.

Abstract Since mineral deposits are the products of multiple hydrothermal pulses, in many circumstances, selecting a robust mineral to date the different mineralization events precisely is important. Vesuvianite, usually known as a rock-forming or accessory silicate mineral typically found in metasomatic and regional metamorphic calcsilicate rocks, has the potential to be a dating mineral. Vesuvianite crystallized entirely from saturated boiling hydrothermal fluid has not been previously reported. Here, we report a new occurrence of hydrovesuvianite, which yields a reliable U-Pb isotope age, is associated with quartz and zircon in hydrothermal veins in central Madagascar. The hydrovesuvianite and associated minerals entirely crystallized from a boiling hydrothermal fluid with relatively low salinities at 290–320°C and 70 bars. The hydrovesuvianite has cell parameters of a 15.6254(5), c 11.8870(9) Å, and space group P4/nnc. The chemical composition of the hydrovesuvianite is similar to vesuvianites of metamorphic origin, and they have LREE-enriched chondrite-normalized rare earth element (REE) patterns and negative Eu anomalies. The hydrovesuvianite crystallized at 526.7 ± 3.6 Ma. Hydrothermal vesuvianite is an ideal U-Pb isotope dating mineral for hydrothermal mineralization and vesuvianite-bearing metamorphic rocks.

Abstract The Eastern Alps have undergone lateral extrusion since the Late Oligocene, with major crustal-scale strike-slip faults still active, as evidenced by earthquakes up to M6, despite scant geological record. Research has focused more on the Salzach-Ennstal-Mariazell-Puchberg (SEMP) and Mur-Mürz faults, leaving the central part of the Northern Calcareous Alps cut by the 110 km long Königssee–Lammertal–Traunsee (KLT) fault system under-studied. We took advantage of a cave environment isolated from erosion, providing unparalleled structural indicators exposure to fill the Pleistocene deformation history gap of the KLT. We reconstruct paleostress for twenty-six reverse, strike-slip, and oblique reactivated faults that offset passages in seven caves close to sinistral KLT and dextral Lammertal faults. 230Th/U dating of faulted and broken speleothems revealed three reactivation events since the Middle Pleistocene. The oldest event could be pinpointed to 560 ka (+100/−60). The middle event dates can be constrained to 331 (+89/−54) to 287 ± 6 ka, or 297–281 ka if the KLT and Lammertal faults were reactivated simultaneously. The youngest event occurred between 130 and 90 ka, aligning with fault reactivations in the Eastern Alps. Cave observations allowed us to analyze reverse faults in the positive flower structure of the KLT and mode I fracture with minor antithetic dextral slip, suggesting a sinistral component of regional rejuvenation. Our findings indicate that the KLT was reactivated due to simple shear with NNE compression. Along the Lammertal fault, we recorded a strike-slip regime driven by NNW compression. The KLT and Lammertal faults form a system of conjugated shears that efficiently accommodate N-S shortening compared to the SEMP fault, which is perpendicular to the compression. Combining our neotectonic data with current seismicity shows that the KLT plays a key role in the Quaternary extrusion process in the studied Alpine sector, surpassing the more prominent SEMP fault.