Search Results (109)

The Mw 7.8 Gorkha Earthquake of 25 April 2015 triggered over 25,000 landslides across central Nepal, with 4775 events concentrated in Gorkha District alone. Despite substantial advances in landslide susceptibility mapping, existing studies often overlook the compound role of post-seismic rainfall and lack robust spatial validation. To address this gap, we validated an ensemble machine learning framework for co-seismic landslide susceptibility modeling by integrating seismic, geomorphological, hydrological, and anthropogenic variables, including cumulative post-seismic rainfall. Using a balanced dataset of 4775 landslide and non-landslide instances, we evaluated the performance of Logistic Regression (LR), Random Forest (RF), and eXtreme Gradient Boosting (XGBoost) models through spatial cross-validation, SHapley Additive exPlanations (SHAP) explainability, and ablation analysis. The RF model outperformed all others, achieving an accuracy of 87.9% and a Receiver Operating Characteristic (ROC) Area Under the Curve (AUC) value of 0.94, while XGBoost closely followed (AUC = 0.93). Ensemble models collectively classified over 95% of observed landslides into High and Very High susceptibility zones, demonstrating strong spatial reliability. SHAP analysis identified elevation, proximity to fault, peak ground acceleration (PGA), slope, and rainfall as dominant predictors. Notably, the inclusion of post-seismic rainfall substantially improved recall and F1 scores in ablation experiments. Spatial cross-validation revealed the superior generalizability of ensemble models under heterogeneous terrain conditions. The findings underscore the value of integrating post-seismic hydrometeorological factors and spatial validation into susceptibility assessments. We recommend adopting ensemble models, particularly RF, for operational hazard mapping in earthquake-prone mountainous regions. Future research should explore the integration of dynamic rainfall thresholds and physics-informed frameworks to enhance early warning systems and climate resilience. Full article

The NW–SE-trending Firenze-Pistoia Basin (FPB) is an intermontane tectonic depression in the Northern Apennines (Italy) bounded to the northeast by a SW-dipping normal fault system. Although it has moderate historical seismicity (maximum estimated Mw 5.5 in 1895), the FPB lacks detailed characterization of its recent tectonic structures, unlike those of nearby basins that have produced Mw > 6 events. This study focuses on the southeastern sector of the basin, including the urban area of Florence, using tectonic geomorphology derived from remote sensing, in particular LiDAR data, field verification, and high-resolution geophysical surveys such as electrical resistivity tomography and seismic reflection profiles. The integration of these techniques enabled interpretation of the subdued and anthropogenically masked tectonic structures, allowing the identification of Holocene activity and significant, although limited, surface vertical offset for three NE–SW-striking normal faults, the Peretola, Scandicci, and Maiano faults. The Scandicci and Maiano faults appear to segment the southeasternmost strand of the master fault of the FPB, the Fiesole Fault, which now shows activity only along isolated segments and cannot be considered a continuous active fault. From empirical relationships, the Scandicci Fault, the most relevant among the three active faults, ~9 km long within the basin and with an approximate Late Quaternary slip rate of ~0.2 mm/year, might source Mw > 5.5 earthquakes. These findings highlight the need to reassess the local seismic hazard for more informed urban planning and for better preservation of the cultural and architectural heritage of Florence and the other artistic towns located in the FPB. Full article

As a strategic replacement area for hydrocarbon exploration in the Tarim Basin, the Kuqa Depression has been the subject of relatively limited research on the sedimentary characteristics of the Triassic strata within its western Wushi Sag, which constrains exploration deployment in this region. This study focuses on the Wushi Sag, systematically analyzing the sedimentary facies types, the evolution of sedimentary systems, and the distribution patterns of the Triassic Kelamayi and Huangshanjie formations. This analysis integrates field outcrops, drilling cores, wireline logs, and 2D seismic data, employing methodologies grounded in foreland basin theory and clastic sedimentary petrology. The paleo-geomorphology preceding sedimentation was reconstructed through balanced section restoration to investigate the controlling influence of foreland tectonic movements on the distribution of sedimentary systems. By interpreting key seismic profiles and analyzing vertical facies successions, the study classifies and evaluates the petroleum accumulation elements and favorable source–reservoir-seal assemblages, culminating in the prediction of prospective exploration areas. The research shows that: (1) The Triassic in the Wushi Sag mainly develops fan-delta, braided-river-delta, and lacustrine–shallow lacustrine sedimentary systems, with strong planar distribution regularity. The exposed strata in the northern part are predominantly fan-delta and lacustrine systems, while the southern part is dominated by braided-river-delta and lacustrine systems. (2) The spatial distribution of sedimentary systems was demonstrably influenced by tectonic activity. Paleogeomorphological reconstructions indicate that fan-delta and braided-river-delta sedimentary bodies preferentially developed within zones encompassing fault-superposition belts, fault-transfer zones, and paleovalleys. Furthermore, Triassic foreland tectonic movements during its deposition significantly altered basin configuration, thereby driving lacustrine expansion. (3) The Wushi Sag exhibits favorable hydrocarbon accumulation configurations, featuring two principal source–reservoir assemblages: self-sourced structural-lithologic gas reservoirs with vertical migration pathways, and lower-source-upper-reservoir structural-lithologic gas reservoirs with lateral migration. This demonstrates substantial petroleum exploration potential. The results provide insights for identifying favorable exploration targets within the Triassic sequences of the Wushi Sag and western Kuqa Depression. Full article

The complex geological environment in western Sichuan, China, leads to frequent debris flow disasters, posing significant threats to the lives and property of local residents. In this study, debris flow susceptibility models were developed using three machine learning algorithms: Support Vector Machine (SVM), Random Forest (RF), and Extreme Gradient Boosting (XGBoost). The models were trained with data in Songpan County and used for debris flow susceptibility prediction in Mao County, using small watersheds as assessment units. Seventeen key feature factors based on multi-source remote sensing data encompassing topography and geomorphology, geological structures, environmental elements, and human activities were selected as input parameters after assessment with Pearson correlation analysis. Model performance was rigorously evaluated through ten-fold cross-validation, and hyperparameter optimization was employed to enhance predictive accuracy. To assess the models’ robustness, the trained models were applied to the neighboring Mao County for cross-regional validation. The results consistently indicate that elevation, seismic nucleation density, population density, and distance to roads are the primary controlling factors influencing susceptibility. Comparative analysis between the Songpan and Mao County reveals that the RF model significantly outperforms SVM and XGBoost in accuracy and robustness. Therefore, the RF model is better suited for debris flow susceptibility assessment in western Sichuan. Although the effectiveness of this model may be limited by the relatively small sample size of debris flow events in the dataset and potential variations in environmental conditions across different regions, it still holds promise for providing a scientific basis and decision-making support for disaster mitigation in comparable areas of western Sichuan. Full article

Geoarchaeological work and excavations of the Helike Project over the last 30 years in the Helike coastal plain, Gulf of Corinth, have yielded abundant evidence on ancient settlements, as well as the surrounding landscape and environmental changes that resulted from geological phenomena and catastrophic events. The research methods applied by the Helike Project followed a multidisciplinary approach, including combined archaeological excavations and palaeoseismological trenching, geophysical prospection, archaeometric, environmental, and soil micromorphology analyses, and computer-based landscape modelling. A wealth of settlement remains that were unearthed across the plain, ranging in date from the Early Helladic period (3rd millennium BC) to the Late Antiquity (5th century AD), indicates that the ancient inhabitants of the area chose to always resettle in the area by adjusting their ways of living to the geomorphology and natural hazards, prevailing each time. Our results show that disasters in the area increased between the Geometric and Roman times due to severe earthquakes that occurred approximately every 300 years. In particular, archaeological and geological finds recovered from the Late Classical–Hellenistic Helike settlement, which was revived in the western part of the plain shortly after the disastrous 373 BC earthquake, have enriched our knowledge regarding the historical seismicity of the region and past human–environment relationships. Full article

Urban expansion in coastal areas involves infrastructure development, industrial growth, and mining activities. These coastal environments face various environmental and geological hazards that require geo-engineers to devise solutions. An integrated geophysical approach aims to address such complex challenges as sea level rise, sea water intrusion, shoreline erosion, landslides and previous anthropogenic activity in coastal settings. In this study, the proposed methodology involves the systematic application of geophysical methods (FDEM, 3D GPR, 3D ERT, seismic), starting with a broad-scale survey and then proceeding to a localized exploration, in order to identify lithostratigraphy, bedrock depth, sea water intrusion and detect anthropogenic buried features. The critical aspect is to leverage the unique strengths and limitations of each method within the coastal environment, so as to derive valuable insights for survey design (extension and orientation of measurements) and data interpretation. The coastal zone of Throrikos valley, Attica, Greece, serves as the test site of our geophysical investigation methodology. The planning of the geophysical survey included three phases: The application of frequency-domain electromagnetic (FDEM) and 3D ground penetrating radar (GPR) methods followed by a 3D electrical resistivity tomography (ERT) survey and finally, using the seismic refraction tomography (SRT) and multichannel analysis of surface waves (MASW). The FDEM method confirmed the geomorphological study findings by revealing the paleo-coastline, superficial layers of coarse material deposits and sea water preferential flow due to the presence of anthropogenic buried features. Subsequently, the 3D GPR survey was able to offer greater detail in detecting the remains of an old marble pier inland and top layer relief of coarse material deposits. The 3D ERT measurements, deployed in a U-shaped grid, successfully identified the anthropogenic feature, mapped sea water intrusion, and revealed possible impermeable formation connected to the bedrock. ERT results cannot clearly discriminate between limestone or deposits, as sea water intrusion lowers resistivity values in both formations. Finally, SRT, in combination with MASW, clearly resolves this dilemma identifying the lithostratigraphy and bedrock top relief. The findings provide critical input for engineering decisions related to foundation planning, construction feasibility, and preservation of coastal infrastructure. The methodology supports risk-informed design and sustainable development in areas with both natural and cultural heritage sensitivity. The applied approach aims to provide a complete information package to the modern engineer when faced with specific challenges in coastal settings. Full article

This investigation presents the current status of seismic sedimentology, along with seismic geomorphology, as applied to the high-resolution (<5 m) mapping of sedimentary facies and hydrocarbon reservoirs in the subsurface. Seismic sedimentology involves the joint investigation of seismic lithology and seismic geomorphology. The high-resolution (as thin as one meter) interpretation of depositional units on lithofacies and paleo-landforms can be achieved by following a comprehensive workflow focusing on three mandatory steps (evaluating and improving data quality; selecting right attributes, preferably 90° seismic trace with frequency fusion; and making use of horizontal resolution on stratal slices) and two optional steps (guiding interpretation with seismic models and applying machine learning techniques). Seismic sedimentology is set to improve through enhanced calibration using well and outcrop data, along with regional and local geological models. Furthermore, there will be a deeper integration between geological and geophysical disciplines, as well as advancements in high-resolution geophysical acquisition and processing techniques. Full article

Objective: The research on turbid current deposition in shallow Marine shelf environments is relatively weak. Method: Based on three-dimensional seismic, drilling and logging data, etc., the spatio-temporal characterization of the shallow sea turbidity current sedimentary system was carried out by using seismic geomorphology and sedimentary numerical simulation techniques. Results and Conclusions: (1) A set of standards for identifying sedimentary units in the X Gas Field was established, identifying four sedimentary units: channel, mound body, channel-side accumulation body, and shelf mud; (2) The vertical evolution and planar distribution of the sedimentary units in the painting were precisely engraved. Along with the weakly–strongly–weak succession of turbidity current energy, the lithological combination of argillaceous siltstone–siltstone–mudstone developed vertically. On the plane, the clusters showed an evolution of isolation–connection–superposition. The scale of the river channel continued to expand, and the phenomena of oscillation and lateral accumulation occurred. (3) Three factors were analyzed: sea level, material sources, and sedimentary substrates (paleo landforms), and a shallow Marine turbidity current sedimentary system was established in the Honghe area in the northwest direction under the background of Marine receding, which is controlled by sedimentary slope folds and blocked by the high part of the diapause during the downward accumulation process of material sources along the shelf. (4) The numerical simulation results reconstructed the process of lateral migration of waterways, evolution of branch waterways into clusters, expansion of the scale of isolated clusters, and connection and superposition to form cluster complexes on a three-dimensional scale. The simulation results are in high agreement with the actual geological data. Full article

A revision of the submarine instability processes offshore the Campania region is presented herein based on the literature data and Multibeam bathymetric and seismic profiles previously acquired by the CNR ISMAR of Naples (Italy). Among others, the objectives and perspectives of this research include the following: the chrono-stratigraphic framework of the submarine instability events and their correlation with the trigger geological processes, including the seismicity, the volcanism and the tectonic activity; density reversal has not been detected as a control factor; the implementation of technologies and database for the acquisition and the processing of morpho-bathymetric, seismo-stratigraphic and sedimentological data in the submarine slopes of Campania, characterized by submarine gravitational instabilities. Other main tasks include producing thematic geomorphological maps of the submarine slopes associated with instability phenomena. The principles of slope stability have been revised to be independent of the slope height. In submarine slopes mainly composed of sand, the stability depends on the slope inclination angle concerning the horizontal (β), equal or minor to the internal friction angle of loose sand (ϕ). Based on this research, it can be outlined that the submarine instability processes offshore of Campania mainly occur along the flanks of volcanic edifices, both emerged (Ischia) and submerged (Pentapalummo, Nisida, Miseno, Procida Channel), on steep, tectonically-controlled sedimentary slopes, (southern slope of Sorrento Peninsula, slope of the Policastro Gulf), and on ramps with a low gradient that surround wide continental shelves (Gulf of Salerno). Full article

The northwestern slope of the Dongdao Platform in the Xisha Sea exhibits a complex geomorphological structure. Utilizing high-resolution multibeam bathymetric data and 2D seismic profiles, this study systematically reconstructs the slope morphology and its evolutionary processes. The study area displays a distinct threefold zonation: the upper slope (160–700 m water depth) has a steep gradient of 15°–25°, characterized by deeply incised V-shaped channels and slump deposits, primarily shaped by gravity-driven erosion; the middle slope (700–1200 m water depth) features a gentler gradient of 10°–15°, where channels stabilize, adopting U-shaped cross-sections with the development of lateral accretion deposits; the lower slope (1200–1500 m water depth) exhibits a milder gradient of 5°–10°, dominated by a mixture of fine-grained carbonate sediments and hemipelagic mud–marine sediments originating partly from the open ocean and partly from the nearby continental margin. The slope extends from 160 m to 1500 m water depth, hosting the C1–C4 channel system. Seismic facies analysis reveals mass-transport deposits, channel-fill facies, and facies modified by bottom currents—currents near the seafloor that redistribute sediments laterally—highlighting the interplay between fluid activity and gravity-driven processes. The slope evolution follows a four-stage model: (1) the pockmark formation stage, where overpressured gas migrates vertically through chimneys, inducing localized sediment instability and forming discrete pockmarks; (2) the initial channel development stage, during which gravity flows exploit the pockmark chains as preferential erosional pathways, establishing nascent incised channels; (3) the channel expansion and maturation stage, marked by intensified erosion from high-density debris flows, resulting in a stepped longitudinal profile, while bottom-current reworking enhances lateral sediment differentiation; (4) the stable transport stage, wherein the channels fully integrate with the Sansha Canyon, forming a well-connected “platform-to-canyon” sediment transport system. Full article

The Jining River northern margin fault is a newly discovered Quaternary active fault, located at the junction of the northeastern corner of the Ordos Block and the Yinshan-Yanshan Uplift (Jining District, Ulanqab, Inner Mongolia). The northeastern margin of the Ordos Block, where the fault is located, is a juxtaposition zone between several active tectonic plates, with widespread active fault distribution and complex tectonic relationships in the region. This study primarily uses seismogeological investigation methods, aiming to reveal the Quaternary activity and seismic hazard of this fault, providing a new analytical perspective on regional seismic activity. Through various methods, geomorphological measurements along the linear scarp of the fault were conducted to determine the distribution of the fault, the surface displacement, and the rupture length caused by its activity. Trenches were excavated at two study sites (Hanqingba and Erjiayan), revealing evidence of paleoearthquake activity. The activity age of the fault was determined through OSL (Optically Stimulated Luminescence) dating of the trench samples. The main conclusions include the following: (1) The fault is a normal fault, spreading along the northern boundary of the Jining Basin, an independent small-scale graben basin in the region, with fault activity controlling basin evolution. (2) The fault was active from the late Middle Pleistocene to the Late Pleistocene, causing scarps in the geomorphology. Since the late Middle Pleistocene, its activity has gradually weakened, with no surface rupture in the Late Pleistocene, and the fault has been inactive in the Holocene. Full article

The Afghanistan earthquake of 21 June 2022 ruptured a ~10 km-long fault segment in the North Waziristan–Bannu fault system (NWBFS) located towards the north of the Katawaz Basin. The earthquake was shallow and reportedly caused widespread devastation. In this article, we investigated the long-term, i.e., geological and geomorphological, evidence of deformation along the earthquake segment. For comparison, we also studied the short-term space geodetic and remote sensing results documenting a visible offset between the fault traces. Focusing on the fault modelling and on the published results, it is thus clear that the earthquake rupture did not reach the surface; instead, it stopped in the shallow sub-surface at ~1 km depth. Moreover, the InSAR analyses show some technical issues, such as coherence loss, etc., likely due to severe ground-shaking leaving some gaps in the results; geological and geomorphological evidence complemented this information. As an outcome of this research, we confirmed that InSAR results could generally capture the overall fault geometry at depth, even in cases of blind faulting, whereas the detailed geometry of the tectonic structure, in this case with a right stepping en-echelon pattern, could be successfully captured by combining it with geological and geomorphological approaches and optical remote sensing observations. Accordingly, the right stepping fault generates a restraining bend in the dominantly left-lateral shear zone. Therefore, such fault stepovers are capable of localizing strain and could act as loci for seismic ruptures, bearing strong implications for the seismic hazard assessment of the region, as well as of other strike-slip fault zones. Full article

Seismic sedimentology and sequence stratigraphy, as emerging interdisciplinary fields, demonstrate unique advantages in characterizing seismic geomorphological responses of various system tracts within the stratigraphic frameworks of rift lacustrine basins. Focusing on the Paleogene Dainan Formation in the Gaoyou Sag of the Subei Basin, eastern China, this study integrates seismic termination patterns, sedimentary cyclicity analysis, and well-to-seismic calibration to subdivide the formation into three third-order sequences containing lowstand (LST), transgressive (TST), and highstand (HST) system tracts. The distribution of five distinct sedimentary facies exhibits pronounced sub-tectonic zonations controlled by the basin’s architecture and structural evolution, with steep slope zones dominated by nearshore subaqueous fan–fan delta complexes, gentle slopes developing normal deltaic systems, and deep-semi-deep lacustrine facies with slump turbidite fans concentrated in depositional centers. Through a novel application of 90° phase adjustment, spectral decomposition, and multi-attribute fusion techniques, the relationship between seismic amplitude attributes and lithologies are established via seismic lithology calibration. Detailed sequence evolution analyses and seismic geomorphological interpretation systematically elucidate the spatio-temporal evolution of depositional systems within different system tracts in rift lacustrine basins, providing a novel methodological framework for sequence stratigraphic analysis in continental rift settings. Full article

The Muong La–Bac Yen–Cho Bo fault is one of the seismic faults in the northwest region of Vietnam. Neo-tectonic activities and exogenous processes have influenced the drainage system and topographic–geomorphologic features on both walls of the fault. The results of topographic analysis and geomorphological indices have confirmed the active tectonics of the fault during the Neo-tectonic period (Pliocene–Quaternary, about 5 million years). The valley floor width-to-height ratio (V_f) of less than 0.5 indicates the “rejuvenation” of the streams and the obvious influence of tectonic activities on the two walls of the studied fault. The Hypsometric curve (HC) in the study area has a straight–convex shape and the basins on the northeast wall have hypsometric integral index values ranging from 0.46 to 0.481, which are lower and more convex than those of the southwest wall. The Mountain-front sinuosity index (S_mf) from 1.92 to 3.28 along the foot slope of the Hoang Lien Son range (the segment from Than Uyen to Bac Yen and Phu Yen) and the highly variable stream-length gradient index (SL) value on the northeast wall signify the relative tectonic uplift on the northeast wall of the fault. The deformed geomorphological indications (steep cliffs, slip surfaces, etc.) in the field confirm the active tectonics of the Muong La–Bac Yen–Cho Bo fault during the Neo-tectonic period. Full article

Geological and topographic site effects lead to variations in the spatial distribution of ground motion during large earthquakes. Despite the impact of such phenomena, they remain poorly understood. There is a lack of joint studies of numerical predictions and experimental observations on the geomorphological site effects. Therefore, a comparison between well-constrained models and experimental field observations is needed. Byblos is a seismic region in Lebanon surrounded by faults that historically generated destructive earthquakes. Its geological and geomorphological settings are interestingly characterized by fractured rocks and anthropic deposits altering seismic ground motions. Field surveys in Byblos gathered ambient vibration recordings and surface waves. It identified multiple resonant frequency peaks, suggesting impedance contrasts and lateral variations in subsurface stiffness, using Horizontal-to-Vertical Spectral Ratio (HVSR) and directivity. It also revealed soft, shallow layers with low velocities, indicating potential resonance during earthquakes, using Multichannel Analysis of Surface Waves (MASW) and 2D seismic arrays. Thus, our study on Byblos is a first step for seismic microzoning of the area that evaluated its heterogeneous subsoil, soft surface layers, and anthropic deposits. Finally, combining geophysical data and field measurements with a numerical model allowed a better understanding of Byblos seismic hazards and enhanced its resilience and sustainability. Full article