Search Results (186)

Slow earthquakes represent an important mode of fault slip transitional between stable creep and dynamic rupture. Their occurrence is jointly controlled by mineral composition, pore-fluid pressure, effective normal stress, system stiffness, and microstructural evolution. Because the internal state of natural faults cannot be directly observed, studies of slow slip, tectonic tremor, and low-frequency earthquakes have long been challenged by weak signals, complex noise, and discrepancies in observational scales. Building on the physical foundations of rock friction and slip stability, this review summarizes recent applications of deep learning to laboratory friction and acoustic data, natural seismic waveforms, Global Navigation Satellite System (GNSS) observations, and strain measurements, with particular emphasis on event detection, fault-state estimation, rate-and-state friction parameter inversion, and forecasting of slip evolution. Existing studies have progressed from event identification to the reconstruction of shear stress, estimation of frictional parameters, and prediction of future fault states. Nevertheless, applications to natural faults remain dominated by event detection and catalog construction, whereas parameter inversion and forecasting still rely largely on laboratory experiments or synthetic data. Physics-informed neural networks, transfer learning, reduced-order modeling, and data assimilation provide promising pathways for integrating laboratory experiments, numerical simulations, and natural observations; however, their reliability remains limited by constitutive-model dependence, parameter non-uniqueness, domain shift, and insufficient independent validation. Future work should strengthen multi-observation integration, cross-region validation, and uncertainty quantification, while developing a bidirectional framework linking laboratory experiments, numerical simulations, and natural fault observations. At present, deep learning is better suited to fault-state characterization and probabilistic assessment of slip trends than to deterministic prediction of the exact timing of slow earthquakes. Full article

Overpressure prediction is critical for safe and efficient drilling, yet remains challenging in complex basins with multiple genetic mechanisms. This study systematically investigates the overpressure origins in the Xihu Sag, East China Sea, a prolific hydrocarbon-bearing sag with widespread overpressure and complex pressure regimes. By integrating well logging data and direct pore pressure measurements from nine wells across three major structural units, the Western Slope Belt, the Western Sub-sag and the Central Inversion Belt, a multi-method diagnostic framework is employed. This combines Bowers’ effective stress analysis with sonic-density cross-plots to discriminate between loading and unloading mechanisms. Results show obvious vertical zoning of pore pressure—normal-pressure zone, overpressure zone, and pressure reversal zone—with distinct horizontal heterogeneity. Results reveal a distinct spatial differentiation in dominant overpressure mechanisms. In the Western Slope Belt, overpressure in the deep Pinghu Formation primarily results from a composite of undercompaction (creating initial pressure seals) and subsequent hydrocarbon generation-induced fluid expansion. In contrast, in the Central Inversion Belt and Western Sub-sag, overpressure is predominantly driven by hydrocarbon charging along faults coupled with tectonic compression, with minimal undercompaction signatures. Previous studies on overpressure genesis in the Xihu Sag have largely focused on the Western Slope Belt. This study expands the analytical scope to the Western Sub-sag and Central Inversion Belt, and conducts a systematic comparative analysis of overpressure genesis across multiple tectonic units. The value of this work lies in the systematic application of classical diagnostic methods to fill the regional research gap regarding the overpressure characteristics of the Huagang Formation and the composite nature of overpressure. With accurately constrained genetic mechanisms, the findings can provide support for optimized drilling fluid design and wellbore stability management, and effectively mitigate deep hydrocarbon exploration risks in this sag and analogous overpressured basins. Full article

This study presents a 3D geological model and structural interpretation of the Masa Valverde volcanogenic massive sulfide (VMS) deposit in the Iberian Pyrite Belt. The deposit is hosted by felsic porphyritic volcanic rocks, volcanic tuffs, and black shales. A 3D geological model of the orebodies and host rocks, constructed from 145 drill-core logs, allowed us to build 16 cross-sections spaced 100 m apart and constrain the mineralization geometry and its structural evolution. Mineralization formed during Early Carboniferous transtensional tectonics within an extensional basin, where an extensional duplex structure controlled the development of the primary massive sulfide body and its associated stockwork. Subsequent counterclockwise rotation of the principal stress axes reactivated extensional faults as reverse faults during tectonic inversion. This deformation strongly modified the VMS system through buttressing, generating extensive open spaces, and promoting the brecciation and recrystallization of both the stockwork and massive sulfides. These processes produced a new paragenesis dominated by chalcopyrite and sphalerite, with minor galena among other minerals, which cemented the breccias, partially replaced earlier mineral assemblages, and filled open fractures. The resulting Cu-Zn enrichment, spatially associated with buttressed zones, provides new insights into ore remobilization with direct implications for the development of the ongoing underground mine. Full article

The spatial distribution of strata under nappe tectonic conditions is highly complex. Conventional approaches, such as dense borehole exploration or intensive in situ investigation, are often costly and difficult to implement for revealing detailed stratigraphic structures. To address this issue, this study focuses on the nappe tectonic setting of the main orebody in the Kambove mining area and proposes a spherical radial basis function interpolation method incorporating spatial anisotropy to construct a three-dimensional resistivity model, thereby providing a data foundation for subsequent intelligent stratigraphic identification. First, the discrete resistivity measurement points were processed through coordinate unification, elevation correction, and data quality inspection. Then, based on radial basis function interpolation theory, a spherical kernel function and anisotropic ellipsoidal constraints were introduced to achieve the three-dimensional continuous representation of discrete resistivity data. Finally, the interpolation performance of the proposed method was compared with that of linear RBF interpolation and inverse distance weighting with $P=2$ and $P=3$ using random holdout validation. The spherical RBF method yielded an ME of −12.2 Ω·m and the lowest RMSE of 299.0 Ω·m, corresponding to RMSE reductions of 13.6–22.0% relative to the comparison methods. These results indicate that the spherical RBF method provides better local interpolation performance within areas covered by existing measurements. The proposed method preserves the continuity and smoothness of the resistivity field and enhances its representation along the dominant geological structural direction, thereby providing a continuous three-dimensional resistivity basis for subsequent intelligent stratigraphic identification. Full article

Dixie Valley, located in west-central Nevada within the Basin and Range Province, is one of the most important geothermal systems in the western United States and an increasingly attractive target for critical-mineral exploration. The valley combines active extensional tectonics, major range-front and intrabasin fault systems, high heat flow, hydrothermal alteration, and thick sedimentary basins that may provide favorable conditions for the development of geothermal reservoirs and lithium-bearing brines or clays. This paper presents an integrated multiphysics interpretation of gravity, magnetic, helicopter-borne time-domain electromagnetic (HeliTEM), and magnetotelluric (MT) data from Dixie Valley, with emphasis on the Grover Point area investigated by the Basin and Range Investigation for Developing Geothermal Energy (BRIDGE) program. We apply joint Gramian inversion of gravity and magnetic data to recover mutually consistent density and magnetization models, including separate induced and remanent magnetization components. We also perform rigorous 3D inversion of HeliTEM data and cooperative 3D inversion of HeliTEM and MT data to obtain a resistivity model extending from the shallow basin fill to deeper fault-controlled geothermal structures. The integrated interpretation identifies low-density sedimentary basins, induced magnetization highs related to magnetic basement or intrusive rocks, remanent magnetization variations associated with basement architecture and hydrothermal alteration, and conductive corridors interpreted as clay-rich alteration zones and possible hydrothermal pathways. These results demonstrate that integrated gravity, magnetic, HeliTEM, and MT inversion can substantially reduce interpretation ambiguity and improve targeting of concealed geothermal systems and associated lithium resources in extensional terranes. Full article

The Songpan-Ganzi and Eastern Kunlun region on the northern margin of the Tibetan Plateau is a key area for the evolution of the Paleo-Tethys tectonic domain and hosts abundant gold, lithium, and polymetallic mineral resources. To reveal the deep structure of this region and its metallogenic background, this study constructed a lithospheric electrical structure model based on magnetotelluric (MT) data along a profile traversing tectonic units such as the Qiangtang, Songpan-Ganzi, and Eastern Kunlun blocks. Data processing, dimensionality analysis, and two-dimensional inversion were performed. The results show that a large-scale, funnel-shaped conductor, originating from the upper mantle and penetrating the middle-lower crust, exists beneath the Songpan-Ganzi and Qiangtang terranes, indicating a major channel for deep-seated thermal material upwelling. Driven by Cenozoic tectonic reactivation, the thermal materials ascended along pre-existing lithospheric weak zones formed during the closure of the Paleo-Tethys Ocean. It spread extensively within the upper-middle crust of the Songpan-Ganzi terrane and migrated to the Eastern Kunlun orogenic belt via complex fault systems, ultimately forming low-resistivity bodies that closely coincide with the locations of major shallow ore-controlling faults. This electrical model suggests the presence of a “thermal material channel” system extending from the mantle to the shallow crust. The study suggests that the migration pathways of ore-forming fluids, represented by gold deposits in the Eastern Kunlun metallogenic belt, are highly correlated with the fault-magma channel system constituted by intra-crustal conductors. In contrast, the lithium-rich granitic magmatism associated with lithium mineralization within the Songpan-Ganzi terrane may be related to the deep thermal background reflected by the large-scale conductor in the upper mantle. From the perspective of electrical structure, this study suggests that mineralization in this region may be closely linked to deep crust–mantle processes. The reactivation of pre-existing tectonic-magmatic channels by Cenozoic thermal material is key to controlling the distribution pattern of dominant shallow mineral resources. The research results provide important geophysical constraints for a deeper understanding of the tectonic–magmatic–mineralization coupling mechanism on the northern margin of the Tibetan Plateau. Full article

In this study, three-dimensional P- and S-wave velocity structures and P- and S-wave velocity ratio variations in the crust and upper mantle beneath the Marmara Region and the Sea of Marmara were modeled using the Poisson tomography method in the field of Seismology. Within this scope, P- and S-wave arrival times from a total of 23,672 earthquakes that occurred in the region between 2011 and 2023 were evaluated, and an inversion procedure based on body-wave arrival times was applied. The obtained results indicate that the northern branch of the North Anatolian Fault Zone is the most active segment among its three main branches. In addition, a low-velocity zone characterized by seismic gap features extending from the southern parts of Marmara toward Istanbul was identified. Within these seismic gap zones, P- and S-wave velocities decrease sharply across regions exhibiting strong velocity gradients. It was determined that this low-velocity structure cuts across the North Anatolian Fault, which branches into three segments within the Sea of Marmara, and continues at depths of approximately 15–25 km. Earthquakes were observed to concentrate particularly in areas with high-velocity ratio variations and within transition zones from low to high values. Due to the complex tectonic and stratigraphic structure of the Marmara Region, these low-velocity seismic gap zones within the crust may be associated with segments capable of generating large earthquakes in the future. Therefore, a detailed investigation of the crustal structure of the region provides important insights for understanding regional earthquake hazards. Full article

Current research suggests that the uranium enrichment in the Qianjiadian deposit, southwestern Songliao Basin (China), is closely related to hydrocarbon dissipation and deep thermal fluids. However, previous investigations have not carried out systematic in-depth research on the abundant calcite veins hosted in diabase within the ore district, especially regarding their types, genetic mechanisms, formation ages, and genetic links to uranium enrichment. In particular, whether their genesis is associated with the two critical ore-controlling factors (hydrocarbon dissipation and thermal fluid activities) remains poorly constrained and to be elucidated. Through analyses of major and trace element geochemistry, scanning electron microscopy, and fluid inclusion microthermometry on calcite veins within fractures of Lower Cretaceous diabase, this study confirms that the veins are products of epigenetic fluid infill with a medium-to-low temperature hydrothermal nature (115–215 °C). The direction of fluid migration was from north to south, consistent with the trend of hydrocarbon dissipation. In situ U-Pb dating yields Eocene (~42.9 Ma) and Pleistocene (1.57–2.82 Ma) ages for the calcite veins, which are highly consistent with the timing of diabase intrusion (early Eocene) and the main episodes of uranium mineralization (Eocene–Oligocene and Pleistocene). Carbon and oxygen isotope compositions and inclusion components indicate that the carbon source was mainly derived from dissipated hydrocarbons, rather than from sedimentary diagenesis or direct source rock generation. The C-O isotopic signatures reflect further carbon isotope fractionation following the interaction between dissipated hydrocarbons and groundwater, and the inclusion fluids, composed mainly of hydrocarbon gases and water, suggest that the carbon source for calcite vein formation was provided by dissipated hydrocarbons. The temporal coupling of hydrocarbon dissipation, calcite vein formation, uranium mineralization, and thermal input from diabase intrusion reflects the dynamic processes of basin evolution and tectonic reworking. The key dynamic backgrounds for this series of diagenetic and metallogenic events include Late Cretaceous tectonic inversion, Eocene–Oligocene tectonic uplift and erosion, and Pleistocene differential uplift and subsidence. The thermal effects from hydrocarbon dissipation and diabase intrusion were the primary factors driving the anomalous uranium enrichment that formed this super-large deposit. The formation of the calcite veins, along with their characteristics indicative of medium-to-low temperature hydrothermal activity and hydrocarbon dissipation, provides a critical window for understanding these processes and offers robust scientific evidence for this genetic model. This study, for the first time, systematically reveals that the calcite veins within the diabase of the Qianjiadian uranium mining area are of medium-to-low temperature hydrocarbon-bearing hydrothermal origin, and constrains their formation ages to the Eocene (~42.9 Ma) and Pleistocene (1.57–2.82 Ma), which are highly coupled with diabase intrusion and two episodes of uranium mineralization events. C-O isotopic and fluid inclusion evidence indicates that the formation of calcite veins directly records the process of hydrocarbon dissipation–groundwater mixing, providing a new mineralogical and geochronological evidence chain for thermal–hydrocarbon–uranium-coupled mineralization. Full article

Quantitative stylolite roughness inversion technique (SRIT) is a powerful tool that is increasingly used to determine burial depth and tectonic stress of rocks that contain stylolites. Despite the increasing use of SRIT, there is still a need to validate the accuracy of the method. The presented work aims to evaluate three fundamental questions: (i) Do we need to correct the calculated stress magnitude if the stress field is tilted? (ii) What is the variability of results as a function of sample length, and (iii) how representative are samples for one outcrop? In order to answer these questions, we derive a corrected formula for tectonic stylolite stress inversion that includes tilted principal stresses, we apply the inversion method across multiple scales on single and variable stylolite samples and we evaluate the stress for multiple samples from one outcrop. Our results show that angle correction is needed for strongly tilted samples (to reduce a potential error of up to 50%), that one single stylolite inversion is not representative no matter what the scale, that the inversion accuracy decreases with scale but can be optimized with mean values (down to a length of 20× crossover length) and that at least the orientation of stresses is very consistent within an outcrop. Full article

Deep gas emissions in volcanic and tectonic environments are commonly interpreted as the surface expression of localized deep emitters. This representation is adequate for first-order description, but it is not physically complete. Deep degassing is more appropriately represented as a coupled source–storage–pathway system in which volatile generation, compressible accumulation, phase change, hydraulic communication, and permeability evolution are dynamically linked. Starting from phase-wise mass conservation in deformable porous–fractured media, reduced equations for gas migration, pore-pressure diffusion, and thermo-poro-mechanical coupling are derived, showing how the distinction between gas-mass transport and pressure propagation provides a unified framework for volcanic and tectonic degassing. Deep pressure gradients are shown to arise from the competition between volatile supply and pathway leakance, while episodic discharge can occur when permeability evolves under effective stress, sealing, and failure. A minimal analytical source–storage–pathway model is further derived, yielding explicit criteria for valve onset, source charging and discharge times, and the distinction between pressure-led and mass-led responses. The framework is then applied to the published Campi Flegrei carbon dioxide (${\mathrm{CO}}_2$) diffuse total output record, providing a real-data illustration of slow storage loading and rapid transient discharge. The analysis considers magmatic exsolution, hydrothermal mediation, metamorphic devolatilization, advective–diffusive near-surface filtering, and the inverse problem through which surface fluxes and gas compositions are used to infer deep source properties. The formulation links magmatic degassing, hydrothermal pressurization, tectonic fluid ascent, and fault-valve behavior within a common continuum-physics perspective and identifies the constitutive assumptions that most strongly control interpretation. Full article

The formation of tectonic–magmatic–sedimentary processes during the Permian in the Beishan region represents a highly debated research topic along the southern margin of the Central Asian Orogenic Belt and even globally: does it mark the final subduction and amalgamation of the Paleo-Asian Ocean, or does it instead represent rifting superimposed upon an earlier orogen? New field observations combined with geochemical analyses reveal that the Liuyuan area is dominated by Early Permian basalts, associated with a rifting sedimentary sequence. During the Mid–Late Permian, gabbro–rhyolite associations were emplaced, accompanied by minor lacustrine sedimentation. The late stage was characterized by minor granitic intrusions or dikes with adakitic affinities, culminating in the emplacement of lamprophyre dikes. The basalts and gabbros in the Liuyuan area display mantle-derived geochemical signatures, with compositions intermediate between MORB and OIB. The exposed Permian basalt–rhyolite bimodal magmatic suite represents a genetically integrated rift-related rock series. Geochemical data from the Ordovician granites and schists within the belt reveal adakitic characteristics, implying that the Permian granitic rocks largely represent remelting products of these early granitic and schistose protoliths. Collectively, the lithological characteristics and magmatic associations clearly demonstrate that the tectonic setting during the Early Permian corresponded to a post-collisional extensional environment superimposed upon the early Paleozoic orogenic belt (Caledonian Huitongshan ophiolite–arc accretionary orogen), which subsequently underwent tectonic inversion to form the present-day orogenic structure. This paper proposes a theoretical model wherein the bimodal magmatic suite was generated by the upwelling of enriched asthenospheric mantle material, providing the driving mechanism for rifting. It formed within a post-collisional extensional environment developed over a complex pre-existing orogenic belt and was subsequently inverted, forming the current tectonic belt—a typical intracontinental Pyrenees-type orogeny. Full article

On 29 July 2025, an Mw 8.8 megathrust earthquake occurred offshore of the southeastern Kamchatka Peninsula, ranking among the ten largest earthquakes worldwide since 1900. Due to observational limitations, the rupture characteristics of large earthquakes along the Kamchatka subduction zone and the north–south contrast in earthquake magnitudes remain poorly understood. In this study, we combine InSAR data, GNSS displacements, and teleseismic waveforms to investigate the spatiotemporal evolution of the 2025 mainshock by constructing a curved fault geometry with along-strike and downdip variations and applying finite-fault inversion together with back-projection analysis. The inversion results show that the mainshock was characterized by unilateral rupture propagating from northeast to southwest, with a rupture length of about 560 km, a duration of about 200 s, and dominant slip concentrated at depths of 15–30 km, with a peak slip of about 10 m. Slip was weak during the initial nucleation stage near the hypocenter, whereas the main slip patch was located within a strongly locked region in the southern segment, and the rupture accelerated rapidly after entering that region. The back-projection results indicate that high-frequency radiation mainly migrated southwestward and was concentrated along the boundaries of the large-slip region and possible structural segmentation zones. These results indicate that the rupture behavior of the 2025 mainshock was jointly controlled by curved megathrust geometry and along-strike locking heterogeneity. The north–south contrast in earthquake size along the Kamchatka subduction zone may result from the combined effects of stronger locking and smoother megathrust geometry in the south, versus more complex fault geometry and submarine tectonic features in the north. This study provides new constraints on rupture processes, seismic cycle behavior, and regional seismic hazard along the Kamchatka subduction zone, and offers important implications for understanding the mechanisms and magnitude potential of future great earthquakes in the Kamchatka region. Full article

Fujian Province is located in the southeast coastal region of Mainland China and belongs to the Cathaysia Block (CB). Since the Neoproterozoic, this region has experienced multi-stage tectonic activities, which have formed extensive metallogenic belts, such as the Wuyishan and Nanling metallogenic belts. To clarify deep geodynamic processes and deep metallogenic mechanisms, we determine a high-resolution three-dimensional (3-D) velocity model of the crust and upper mantle beneath the Fujian region. Two datasets are collected for the tomographic inversion. One dataset includes 70,330 P-wave and 87,057 S-wave arrival times from 6206 local earthquakes. The other dataset includes 13,714 P-wave relative travel-time residuals from 812 teleseismic events. Our tomography reveals significant low-velocity (low-V) anomalies in the upper mantle down to 500 km depth, which may represent hot ad wet upwelling flows from the mantle transition zone. We also find some low-V and high-Vp/Vs anomalies in the crust beneath major faults and the coastal area of Fujian, which are interpreted as magmatic channels. Combining with previous geological, geochemical, and geophysical results, we consider that the subduction of the Paleo-Pacific Plate in the Late Mesozoic played a crucial role in the formation of ore deposits. We propose a geodynamic model of the deep mineralization in Fujian, in which upwelling mantle flow underplated the crust and intruded into the crust along fault zones. This geodynamic model also has certain significance for the deep mineralization mechanisms of the CB and the Lower Yangtze Block. Full article

This study investigates the Mw 7.1 earthquake that struck the Southern Tibetan Plateau (Xizang) on 7 January 2025, using joint Interferometric Synthetic Aperture Radar (InSAR) observations and inverse modeling to characterize the fault geometry and slip distribution. Coseismic interferograms derived from Sentinel-1 and ALOS-2 data reveal complex surface deformation patterns, indicating rupture along four distinct fault segments. This configuration provides a more detailed fault segmentation than proposed in previous studies, featuring predominantly normal faulting on a north–south-trending structure consistent with regional extensional tectonics. Integrated analysis of coseismic deformation, source modeling, and Coulomb Failure Function (ΔCFF) stress changes suggests that the three secondary fault segments were potentially activated synchronously with the mainshock, in addition to the principal rupture. The results underscore the complexity of the seismic source and document the activation of an antithetic fault segment, for which the InSAR observations provide compelling quantitative evidence. Full article

East Antarctica is composed of a composite Precambrian shield largely covered by a thick ice sheet. Information on the thermal structure of the East Antarctic lithosphere is critical to the understanding of the geological history and ice sheet dynamics of this region. To better describe the lithospheric thermal structure, Curie-point depths are first estimated through the inversion of aeromagnetic anomaly data using the wavenumber-domain centroid method, and the Curie point estimates is further employed to determine a lithospheric thermal thickness model by integrating the 1D steady-state heat conduction equation. Our results show that the variations in both the Curie-point depth and thermal thickness estimates have strong spatial consistency with known major geological provinces, such as ancient cratons and younger orogens. Moreover, our findings show a hot and thin lithosphere in the Gamburtsev Subglacial Mountains and Dronning Maud Land, whereas a cold and thick cratonic lithosphere is found in the Wilkes and Aurora Subglacial Basins and the hinterland of Enderby Land. A few local-scale thermal anomalies are also observed in cratonic areas, indicating that some of these areas have lost their cratonic signature. The new thermal thickness model provides direct constraints that can be used to trace early tectonic–thermal activities in East Antarctica. Full article