Earthquake-induced fracturing and microcrack development in subsurface strata are widely recognized as important processes influencing seepage and the hydrological behaviour of surface water bodies, particularly in tectonically active mountainous terrains. However, the hydrogeological response to repeated low-magnitude (<4) seismic events remains poorly understood. This study presents an integrated geoelectrical and remote sensing investigation of the Nagi Lake region in the Sikkim Himalaya, India, based on Vertical Electrical Sounding (VES) surveys conducted in May 2022 and March 2026, following a seismic sequence of 74 low-magnitude earthquakes recorded during February 2026. Comparative analysis of four VES profiles (VES1–VES4), supported by validatory factor analysis, reveals spatially heterogeneous changes in subsurface electrical characteristics between the two survey periods. VES1, VES2, and VES3 indicate reduced signatures of pre-existing microcracks that are consistent with sediment densification and partial sealing, whereas VES4 suggests localized development or persistence of microfractures. Because the surveys span approximately four years, these changes likely reflect the combined influence of long-term hydrogeological, environmental, and geomorphic processes, with the February 2026 seismic sequence representing one potential contributing factor rather than the sole driver. To further evaluate ground deformation, Sentinel-1A Synthetic Aperture Radar (SAR) data acquired between January 2019 and March 2026 were analysed using Persistent Scatterer Interferometric SAR (PS-InSAR). The results indicate cumulative Line-of-Sight (LOS) displacements ranging from −17.9 cm (movement away from the satellite) to +3.5 cm (movement toward the satellite) in the vicinity of Nagi Lake, reflecting localized surface deformation with millimetre-scale precision. These observations provide complementary evidence of ongoing subsurface adjustment that may promote sediment compaction and microcrack modification. Overall, the study demonstrates measurable temporal changes in the subsurface structure of the Nagi Lake area and suggests that repeated low-magnitude seismicity may contribute to subsurface restructuring alongside other environmental processes. The findings highlight the value of integrating geophysical monitoring and satellite-based deformation analysis for understanding groundwater–surface water interactions and supporting the sustainable management of vulnerable Himalayan water bodies.
Recent destructive earthquakes have clearly demonstrated that damage distribution in many cities developed on thick alluvial deposits is strongly controlled by local soil amplification and site response effects. Soil conditions therefore play a critical role in determining the characteristics of ground motion and the seismic performance of structures during earthquakes. This study presents the first microzonation-oriented site response assessment for the rapidly urbanizing city of Afyonkarahisar, which is characterized by thick alluvial deposits and a shallow groundwater table. A database consisting of 124 boreholes was compiled to characterize the subsurface stratigraphy of the study area. Shear-wave velocity profiles were verified using both SPT-based correlations and MASW measurements to ensure reliable input parameters for dynamic analyses. One-dimensional equivalent linear and nonlinear site response analyses were performed using the DeepSoil program, employing eleven earthquake ground motion records scaled according to the Turkish Building Earthquake Code. The results indicate that for Earthquake Level-1 (EL-1; 2% probability of exceedance in 50 years) ground motions, nonlinear analyses produce lower amplification factors (1.00–1.62), whereas equivalent linear analyses tend to predict higher amplification values, reaching up to 4.52, owing to their simplified treatment of soil nonlinearity. Under Earthquake Level-2 (EL-2; 10% probability of exceedance in 50 years) motions, both methods yield comparable amplification values ranging from 1.18 to 1.72. GIS-based amplification maps reveal significant spatial variability within the study area and identify zones where local soil conditions may substantially increase seismic demand. The findings suggest that nonlinear site response analysis is more appropriate for representing soil behavior under strong ground motions (EL-1), while both approaches provide comparable results for moderate ground motions (EL-2). Comparisons with Eurocode 8 and NEHRP site classifications further confirm the broader applicability of the results. Overall, this study provides a practical framework for reliable site response assessment that supports earthquake-resistant design and microzonation studies in seismically active regions characterized by complex alluvial environments.
Süleyman Gücek, Ismail Zorluer, K. B. Afacan et al.· Applied Sciences· 0 citations
Geomorphic features, drainage patterns and topography are key indicators of active tectonics. This study examines geomorphological characteristics and geological hazards, specifically earthquakes and landslides, in the Muzaffarabad region. The findings contribute to disaster risk reduction and achievement of sustainable development goals (SDGs). Field‐based geomorphological studies and satellite imagery were used to analyse the geomorphological characteristics of the region. Five geomorphic indices, namely asymmetry factor (AF), drainage basin shape index (Db), slope analysis, valley floor width‐to‐height (
V
f
) ratios and hypsometric curves, were calculated using shuttle radar topography mission digital elevation model (SRTM DEM). Features such as drainage offsets, stream deflections, faceted spurs, seismicity, deformed recent sediments and point bars dissection near the Jhelum and Muzaffarabad faults suggest left‐lateral oblique‐slip motion, indicating the tectonically active nature of these faults. The geomorphic and neotectonics analysis concludes that the Muzaffarabad region is highly susceptible to earthquakes and landslides, particularly, in fault‐affected areas. A flood susceptibility analysis using multi‐criteria decision analysis (MCDA) in ArcGIS was conducted to enhance climate resilience and disaster preparedness (SDG 13) and support (SDG 6) by identifying flood‐prone areas. Three high‐risk flood zones were identified: Neelum River–Shawai Nala confluence, Jhelum–Neelum rivers convergence at Domel and a low‐lying area near the Lohargali landslide. This study highlights the importance of integrating morphometric, geomorphological and geospatial techniques for effective disaster risk reduction (SDGs 11 and 13), climate‐resilient infrastructure (SDG 9), addressing SDG 6 and sustainable urban development, ensuring long‐term safety in tectonically active regions. Additionally, the methodology in this study, integrating multiple existing techniques, can be expanded for hazard assessment in other regions.
Waqar Ayub, Ahmed Nabi, M. Jabran et al.· Geological Journal· 0 citations
Understanding the mechanisms controlling microseismicity in fluid-rich areas is key for assessing seismic hazards and the interaction between tectonics, magmatism, and geothermal systems. The Tuscan Magmatic Province, straddling the Tyrrhenian coast of southern Tuscany and northern Latium in Italy, is an ideal place to study these interactions. This region features high heat flow, extensive hydrothermal fluid circulation and several geothermal systems. However, the role of these fluids in controlling the microseismicity in the area is not fully understood. To shed light on this topic, we deployed a broadband seismic network that integrated the permanent regional networks from September 2020 to September 2021. Using state-of-the-art machine learning detection and probabilistic location methods, we detected and located 1,944 high-quality earthquakes with moment magnitudes ranging from Mw −0.2 to 2.8. By detecting approximately four times more events than reported by the regional catalogue, this new and high-resolution earthquake catalogue for the Southern Tuscany region (Italy) provides a more refined characterization of seismicity within Southern Tuscany’s unique geological framework. Our study reveals strong spatial clustering of seismicity along a NW-SE striking strip, parallel to the Apennines belt, and terminating in correspondence of the Monte Amiata geothermal system. West of this alignment, an additional cluster is associated with the Larderello-Travale geothermal system. Focal mechanisms indicate a coexistence of strike-slip and extensional style of deformation. A most prominent sequence consists of more than 500 events aligned along a NW-SE normal fault and exhibits clear upward hypocenter migration. The estimated velocities of the seismic front are in the order of 200-600 m/h. The calculated hydraulic diffusivities (10-15 m2/s) suggest fluid diffusion as the primary driver of the swarm. This is in agreement with the seismic sequences departing from magmatic bodies. To explain the source of the seismic swarm we propose a valve-type mechanism in which an initial tectonic failure phase progressively opens the fault system, enabling fluid advection that sustains subsequent seismic activity. The spatial correlation between seismicity and low-velocity crustal zones further supports the role of deep fluid circulation. These results show that microseismicity around geothermal systems in Southern Tuscany is shaped by the combined effect of tectonic stress loading and transient fluid overpressure, with implications for seismic hazard assessment and geothermal resource management.
J. Porras, Konstantinos Michailos, Geneviève Savard et al.· Geophysical Journal Internat...· 0 citations
Hydrocarbon production reduces pore-fluid pressure and increases the effective stress acting on the grain framework of reservoir rocks. This process induces reservoir deformation, compaction, and stress redistribution, often manifesting as fault reactivation, surface subsidence, wellbore instability, and 4D seismic time shifts. In this study, we present a geomechanical and structural interpretation of production-induced stress changes in the Kolo-Creek Field, Coastal Swamp Niger Delta, Nigeria. The analysis integrates 3D seismic interpretation, geomechanical evaluation, well-log analysis, and production data. Time-lapse seismic surveys acquired in 1997 (base) and 2009 (monitor) show clear 4D responses with a root-mean-square repeatability ratio (RRR) of 0.38, indicating excellent survey repeatability. The seismic interpretation reveals fault reactivation and fracturing associated with production-induced stress changes. Geophysical well logs from seven wells were used to delineate and correlate three reservoir zones (Sand A, Sand B, and Sand C). Petrophysical analysis indicates low shale content ranging from 7.74–37.44%, high porosity values between 0.19 and 0.36), and excellent permeability varying from 375–3327 mD, which is consistent with high-quality, coarse-grained sandstones. Production and pressure data provided by SPDC show a decline from 1592.55 to 400.34 bbl/day and from 4766 to 3103 psi over 12 years, respectively, corroborating with the geomechanical interpretation. The integration of geomechanics with seismic and structural analysis demonstrates the influence of reservoir stress changes on fault behavior and reservoir performance, providing insights to optimize production and manage risks in similar deltaic settings. This study could lead to Wellbore Stability Management; Using stress change predictions to guide well placement and drilling orientation, minimizing risks of shear failure, casing deformation, and production losses.
Orji Stephen, Tamunobereton-ari Iyenomie, Amakiri Chinoye et al.· Petroleum Science and Engine...· 0 citations
Landslides in deglaciating fjords pose a potential tsunami threat to nearby communities; however, processes contributing to long‐term progressive rock damage and landslide conditioning remain poorly constrained in paraglacial settings. Here, we analyse the role of earthquake‐induced rock mass damage over late Pleistocene to Holocene time scales, as a conditioning factor for modern landslides, using distinct element numerical modelling to assess spatial and temporal patterns of fracture propagation influenced by varying glacier thickness. Conceptualised numerical models were parameterised by in situ rock mass, glacial and topographic conditions in Serpentine valley, located in Prince William Sound, Alaska, where several large landslides are actively developing along the western valley wall. Results show that although rigid glacier buttressing reduces co‐seismic rock mass damage, it does not suppress it completely, and damage occurs both above and below the glacier surface elevation. We demonstrate that topography, and especially steep slopes with topographic convexity, as well as preexisting damage of joint networks and faults inherited from tectonic and exhumation induced stresses, exert primary control on the location of new co‐seismic damage. Simulations representing a simplified deglaciation sequence over the past 25 ka, with a series of 10 evenly spaced earthquakes, generated rock mass damage patterns that qualitatively match in situ landslide structural and kinematic observations at one instability in Serpentine valley. Our conceptual study helps clarify the role of repeated seismicity over glacial timescales as a long‐term conditioning process for paraglacial rock slope failure, highlighting spatial and temporal patterns of progressive damage accumulation, with outcomes relevant for modern landslide hazard assessment.
Molly E. McCreary, J. Moore, E. Jensen et al.· Earth Surface Processes and...· 0 citations
Groundwater occurrence in hard-rock terrains is complex and spatially heterogeneous, controlled by weathered and fractured zones with limited surface expression. This research integrates Vertical Electrical Sounding (VES) with remote sensing, GIS and Analytical Hierarchy Process (AHP) for groundwater potential mapping of Jeypore Block, Koraput District, Odisha. This area is underlain by Eastern Ghats Mobile Belt rocks such as khondalites, charnockites, and granite gneisses. Fifteen VES surveys using Schlumberger configuration were conducted across the study area, with electrode spreads up to 800 m. Resistivity data were interpreted using IPI2WIN software, producing one-dimensional resistivity models and Dar-Zarrouk parameters. Subsurface profiling revealed distinct lithological layers consisting of topsoil, laterite, sandstone, weathered/fractured granite, and compact bedrock. Layer thicknesses ranged from 0.6 to 20.4 m in the first layer to 99.5 m in the third layer. Iso-resistivity maps generated using Surfer-25 showed significant lateral heterogeneity. Low-resistivity zones (2.6–105.2 Ωm) indicated saturated formations, whereas high-resistivity values (> 150 Ωm) represented compact basement rocks. Curve-type analysis identified predominantly AAA-type curves, which indicate increasing resistivity with depth. HA-type curves observed at two locations suggested the presence of conductive, water-saturated layers favourable for aquifer development. VES-derived parameters were integrated with twelve geospatial thematic layers, including geology, geomorphology, soil, NDVI, lineament density, drainage density, rainfall, slope, physiography, land use, groundwater fluctuation, and hydrogeology, using the AHP framework. The consistency ratio of the model was 2.36%, indicating reliable thematic weighting. Validation via pumping tests and ROC analysis (AUC = 0.86) confirmed model reliability. This approach offers a scientifically robust framework for sustainable groundwater management in structurally complex hard-rock terrains.
