Seismic Hazard Research Articles

Abstract We present a multiscale seismic attenuation tomography of a seismotectonically complex region in northern Italy hosting the well‐characterized Collalto Underground Gas Storage (UGS). Beyond its specific relevance, this site provides a natural laboratory for assessing the ability of attenuation imaging to distinguish fluid‐rich zones from highly strained, failure‐prone volumes. We integrated scattering and absorption tomography models: scattering anomalies, between the two principal thrusts, highlight localized strain near fault tips; absorption tomography images the shallow UGS and reveals a deeper fluid‐saturated volume. Seismicity concentrated around this deeper anomaly, exhibiting a pulsatory temporal pattern, suggests a fluid‐driven role in the deformation processes. These findings show that attenuation tomography, combined with multiscale and complementary geophysical models, can resolve critical subsurface features related to fluids and strain. The approach is broadly applicable to geothermal and volcanic contexts and supports seismic hazard assessment in tectonically active regions where natural and anthropogenic processes may interact.

Ground Penetrating Radar (GPR) is a powerful tool for imaging shallow stratigraphic and structural features. This study shows that it is particularly effective also in detecting near-surface evidence of active faulting. In the Southern Apennines (Italy), one of the most seismically active regions of the Mediterranean area, the shallow expression of active faults is often poorly constrained due to limited or ambiguous surface evidence. Low-frequency GPR profiles were acquired in the Calore River Valley (Campania Region), an area historically affected by large earthquakes and characterized by debated seismogenic sources. The surveys employed multiple antenna frequencies (30, 60, and 80 MHz) and both horizontal and vertical acquisition geometries, enabling penetration depths ranging from ~5 m to ~50 m. The acquired GPR profiles, integrated with high-precision georeferencing, were able to reveal the presence of shallow steeply dipping active normal faults striking E–W to ENE–WSW, here named the Postiglione Fault System. Therefore, this study highlights the methodological potential of low-frequency GPR for investigating active faults in carbonate substratum and fine-to-coarse-grained sedimentary units and thus contributing to refining the seismotectonic framework and improving seismic hazard assessment of seismically active areas such as the Southern Apennines.

The Longshou Shan area is located on the northeastern margin of the Tibetan Plateau in northwest China. The study area is located where the sinistral Altyn Tagh and Haiyuan Faults overlap and the Qilian Shan thrust fault systems in the northeastern Kunlun–Qaidam Block converge. This region experiences frequent seismic events, including large-magnitude earthquakes, which are significant indicators of ongoing tectonic deformation and stress accumulation in the Earth’s crust. The seismicity of Longshou Shan is not only a consequence of its tectonic setting but also a key factor in understanding the seismic hazard posed to the surrounding areas. The tectonic activity within the Longshou Shan region of NW China is a focus of our geomorphological research due to its significance in understanding the complex interactions between tectonic forces and surface processes. Situated on the northeastern edge of the Tibetan Plateau and along the eastward trace of the Altyn Tagh Fault, Longshou Shan is crucial for investigating the plateau’s northward expansion. This study leverages ALOS-based digital elevation models (DEMs) and geomorphic indices to evaluate the tectonic activity in the area, employing various indices such as mountain front sinuosity, valley floor width-to-height ratio, hypsometric curves, asymmetry factors, basin shape indices, and channel steepness index to provide a comprehensive tectonomorphological analysis. Our results indicate intense tectonic activity on both sides of Longshou Shan, making it a highly hazardous seismic area. We also highlight the importance of thrust faults and related crustal shortening in the formation and expansion of the plateau.

Alleviating post-injection seismic hazard in enhanced geothermal systems: Insights from a multi-scale study

Frictional stability of Pelona–Orocopia–Rand schists under hydrothermal conditions and implications for seismic hazards in Southern California

This study investigates spatiotemporal b value variations and seismic interaction networks preceding the Mwg 7.1 Dingri earthquake that struck southern Tibet on 7 January 2025. Using relocated earthquake catalogs (2021–2025) and dual-method analysis combining b value mapping with Granger causality network modeling, we reveal systematic precursory patterns. Spatial analysis shows that the most significant b value reduction (Δb > 0.5) occurred north of the mainshock epicenter at seismogenic depths (5–15 km), closely aligning with subsequent aftershock concentration zones. Granger causality analysis reveals a progressive network simplification: from 73 causal links among 28 nodes during the background period (2021–2023) to 49 links among 34 nodes pre-mainshock (2023–2025) and finally to 6 localized links post-rupture. This transition from distributed system-wide interactions to localized “locked-in” dynamics reflects the stress concentration onto the primary asperity approaching critical failure. The convergence of b value anomalies and network evolution provides a comprehensive framework linking quasi-static stress states with dynamic system behavior. These findings offer valuable insights for understanding earthquake nucleation processes and improving seismic hazard assessment in the Tibetan Plateau and similar complex tectonic environments.

Abstract Seismic hazard mapping is crucial for earthquake preparedness and mitigation, specifically in the Himalayan Belt. Because several factors must be evaluated throughout the evaluation process, it can be represented as a multiple-criteria decision-making (MCDM) problem. In this study, we have applied the integrated Analytical Hierarchy Process-Entropy MCDM models to assess the seismic hazard in Sikkim, India. The findings of this study indicate that 43.20% of the total geographical area and 54.64% of the inhabitants reside under the high to very high seismic hazard level. The finding was validated using a receiver operating characteristic curve, showing an accuracy level of 64%, which is satisfactory. This work may be helpful for the government and disaster management agencies to prepare for destructive events that may occur in this belt of the Himalayas.

The 28 March 2025 moment magnitude (Mw) 7.7 earthquake in Mandalay, Burma (Myanmar), ruptured 475 kilometers of the Sagaing Fault, which was more than twice the length predicted by magnitude scaling relationships. Kinematic slip models and observation of a Rayleigh Mach wave that passed through parts of Thailand confirmed that rupture occurred at supershear velocities of greater than 5 kilometers per second. The anomalous length exposed a vast population to violent near-fault shaking. The Mandalay earthquake is a modern analog for the Mw 7.9 1906 San Francisco earthquake, another atypically long and fast rupture. Probabilistic seismic hazard analyses use scaling relations that do not account for such long ruptures at moderate magnitudes. This limitation, in conjunction with a likely increased population and infrastructure exposure for atypically long ruptures, contributes to a potential mischaracterization of seismic risk.

Abstract Simulating the full spectrum of fault slip behavior—from slow aseismic creep to dynamic earthquake rupture—is essential for advancing our understanding of fault mechanics and long‐term seismic hazard. However, few open‐source tools provide efficient three‐dimensional modeling of these processes with the flexibility needed for research across scales. Here we introduce PyQuake3D, an open‐source Python package for simulating fault slip evolution using quasi‐dynamic approximations. The code solves elastic interactions via the boundary element method and incorporates hierarchical matrix compression to reduce memory usage and computational cost. PyQuake3D is designed for scalability and portability, supporting both distributed‐memory parallelism (MPI) and optional Graphics Processing Unit (GPU) acceleration. We validate the code against established sequences of earthquakes and aseismic slip (SEAS) benchmarks and illustrate its ability to capture key phases of the seismic cycle, including nucleation, rupture propagation, arrest, interseismic stress accumulation, and postseismic relaxation. Applications include simulations of faults with spatially heterogeneous friction, a geologically constrained model of the East Anatolian Fault Zone, and a laboratory‐inspired triaxial experiment. These examples demonstrate the ability of PyQuake3D to resolve the spatiotemporal complexity of fault slip, including the interplay of geometry, frictional properties, and loading. By combining scalable numerical techniques with accessible software design, PyQuake3D provides a robust and extensible platform for modeling fault slip dynamics across a wide range of geophysical scenarios.

Abstract This study investigates the Elbistan Earthquake, the second event of an earthquake doublet that struck south‐central Türkiye with magnitudes Mw 7.7 and Mw 7.6, on 6 February 2023. While space‐based geodetic and remote sensing studies have provided information on surface rupture and displacement distribution, detailed rupture strands and ground deformations were not thoroughly documented. To address this gap, we generated a high‐resolution (∼5 cm/px) and continuous 300‐m‐wide strip map along the entire surface rupture. Our mapping reveals a primarily sinistral rupture length of approximately 143 km between Göksun and Gözene, with previously unrecognized faults at the westernmost 4.5 km and easternmost 20 km. In the east, the rupture rotates 42° anticlockwise and propagates NE along an unmapped fault rather than the Sürgü and Doğanşehir faults. The rupture is divided into seven major sections: Göksun, Ericek, Ekinözü, Barış, Nurhak Fault Complexity, Kullar, Gözene and Eskiköy splay. The width of the deformation zone of primary and secondary features varies from a few meters to 1.5 km along these sections. Our analysis of 538 co‐seismic displacements reveal maximum displacement of 10.58 ± 0.3 m in the Ekinözü section. The mean co‐seismic displacement along the rupture is 4.1 m based on a moving mean fit to the displacements. These findings provide crucial insights into the Elbistan Earthquake co‐seismic surface deformation and displacement distribution, enhancing our understanding of the rupture mechanics and contributing valuable high‐resolution data for seismic hazard assessment in the region.

On 6 February 2023, an earthquake doublet of Mw 7.8 and Mw 7.5 occurred in southeastern Turkey and caused surface ruptures over 350 km for the eastern Anatolian fault (EAF) and 150 km for the Surgu fault (SF), respectively. Over 3700 Mw > 3.0 aftershocks occurred within 5 months following the earthquake doublet, indicating that postseismic stress adjustment is evident. Here, we utilize InSAR technology to investigate the earthquake doublet in terms of its coseismic and postseismic deformations and to estimate the changes in Coulomb stress. We found that the postseismic surface deformation is consistent with the coseismic rupture, characterized by left-lateral strike-slip movement. The coseismic deformations (>5 m) are concentrated in the central-eastern (Pazarcik and Erkenek) segments in the EAF and the central (Cardak) segment in the SF. Notably, the maximum coseismic slip (up to 10 m) and the largest postseismic slip (∼0.5 m) both occurred on the Cardak segment. Postseismic deformations (>0.05 m) are concentrated in the northeastern Erkenek segment and southwestern Amanos segment of the EAF, as well as the eastern Dogansehir segment of the SF. Compared with the coseismic deformation, the postseismic slip compensated for the insufficient deeper slip of the southwestern Amanos segment of the EAF and the central Cardak segment of the SF. Additionally, the postseismic slip extended the rupture area to both the northeast of the Dogansehir segment along the SF and the epicentral area of the 2020 Mw 6.7 earthquake along the EAF. The postseismic afterslip largely reduced the potential seismic hazard of the seismic gap between the eastern end of the coseismic rupture of the 2023 Mw 7.8 earthquake and the epicentral area of the 2020 Mw 6.7 earthquake, as well as the southwestern Amanos segment of the EAF and the eastern Dogansehir segment of the SF.

Understanding the role of upper-plate faults in obliquely convergent margins is essential for assessing regional strain distribution and seismic hazards. In the Himalayas, paleoseismic research has focused on the Main Frontal thrust as the primary surface expression of the plate boundary, leaving the seismic potential of upper-plate faults like the Western Nepal fault system largely unstudied. This study presents new paleoseismic evidence from seven trench sites across five mapped fault segments of the ∼250-km-long Western Nepal fault system, providing the first direct constraints on its earthquake history. Stratigraphic and geochronologic data reveal at least three Holocene surface-rupturing earthquakes, with age constraints indicating that at least one of these events overlapped in time with a major Himalayan earthquake within the past ∼800 yr. This demonstrates that the Western Nepal fault system is a significant, cross-orogen fault system, playing an active role in accommodating strain in the region. These findings establish the Western Nepal fault system as an active seismogenic system that accommodates oblique plate convergence and contributes to regional strain partitioning. This challenges the prevailing view that seismic deformation in the Himalayas is primarily confined to the Main Frontal thrust and highlights the need to incorporate upper-plate fault systems into seismic hazard assessments.

Mechanisms of Foreshocks and Seismic Hazards Under Mining-Induced Stress in Longwall Mines

This study investigates the spatial-cognitive representations, emotional responses, levels of disaster preparedness, and institutional expectations of fifth-grade middle school students in Bağcılar, a district of Istanbul that exemplifies urban life under high seismic hazard in Türkiye. Adopting a qualitative case study design, the research employed semi-structured interview forms to collect data, which were subsequently analyzed through content analysis. The results of the study reveal that students exhibit a vivid awareness of earthquake risks; however, this awareness is closely interwoven with intense feelings of anxiety, uncertainty, and perceived inadequacy. Rather than framing earthquakes as geophysical phenomena, students predominantly conceptualize them through their destructive impacts—such as loss of life and property, physical damage to the built environment—and the emotional responses they trigger, including fear, panic, and helplessness. Furthermore, students view disaster response and recovery not merely as matters of individual preparedness, but also as requiring institutional capacity, coordinated governance, and systematic risk-reduction measures led by authorities.

Earthquake-induced soil liquefaction represents a critical geotechnical challenge due to its nonlinear soil–seismic interactions and its impact on structural safety. Traditional empirical methods often rely on simplified assumptions, limiting their predictive capability. This study develops and compares six machine learning (ML) classifiers—namely, Support Vector Machine (SVM), Artificial Neural Network (ANN), k-Nearest Neighbor (kNN), Random Forest (RF), Decision Tree (DT), and Naïve Bayes (NB)—to evaluate liquefaction susceptibility using an original dataset of 461 soil layers obtained from borehole penetration tests in the Edremit region (Balıkesir, NW Turkey). The models were trained and validated using normalized geotechnical and seismic parameters, and their performance was assessed based on accuracy, precision, recall, F1 score, and area under the receiver operating characteristic curve (AUC). Results demonstrate that SVM, ANN, and kNN consistently outperformed other models, achieving test accuracies above 93%, F1 scores exceeding 98%, and AUC values between 0.933 and 0.953. In contrast, DT and NB exhibited limited generalization (test accuracy of 84–88% and AUC of 0.78–0.82), while RF showed partial overfitting. In contrast, DT and NB exhibited weaker generalization, with test accuracies of 84% and 88% and AUC values of 0.78 and 0.82, respectively, while RF indicated partial overfitting. The findings confirm the superior capability of advanced ML models, particularly SVM, ANN, and kNN, in capturing complex nonlinear patterns in soil liquefaction. This study provides a robust framework and original dataset that enhance predictive reliability for seismic hazard assessment in earthquake-prone regions.

Jakarta, which is close to the earthquake path, has a high potential for seismic hazards, so building structures must be designed to withstand earthquakes. The X Building, located in West Jakarta, is expected to have an earthquake-resistant structure, evaluated using pushover analysis. This study aims to assess the performance of the X Building structure against earthquake loads using pushover analysis with ETAS software. X Building underwent translation in patterns 1 and 2, followed by rotation in pattern 3. The value of the structure period in the X direction is 2.578 seconds, and in the Y direction is 2.252 seconds. The mass participation requirement has been met, with a participation rate of 90% or higher in all three directions. There is torsional irregularity in the Y direction. The dynamic shear force after scaling is 10,503.93 kN (X) and 10,503.94 kN (Y). When the performance point is reached, the roof displacement is 623.182 mm (X) and 513.267 mm (Y). The total number of plastic hinges is 2774 in the X direction and 2330 in the Y direction. The structural performance level obtained is Damage Control (DC). The ductility value in the X direction is 1.31, and in the Y direction is 1.12.

ABSTRACT In the last two decades, empirical regressions for the conversions of traditional magnitudes (e.g., ML, Ms, and mb) to moment magnitude Mw were mostly computed using error-in-variable (EIV) method, also known as general orthogonal regression, and not the ordinary least-squares (OLS) method because the uncertainties of traditional magnitudes are not negligible when compared to that of Mw. However, a few recent articles criticized such approaches based on the hypothesis that an error in the equation, that is, the epistemic uncertainty associated with the form of the regression equation, is present, and this is better accounted for by the OLS rather than by the EIV. In this work, we first discuss the problem theoretically and then make some analysis on real datasets. We find that the regression coefficients are strongly influenced by the assumption made about the sizes of the errors of traditional magnitudes. In particular, the role of equation error may be significant if the assumed errors of the traditional magnitudes are small (≤0.1 magnitude units) or may even be almost negligible if the errors are only slightly larger (>0.12–0.15). In general, the EIV method has always to be preferred with respect to OLS, but it might require a small correction for equation error. These findings have significant implications for statistical forecasting and seismic hazard assessment.

This study evaluates the seismic impact of the Bukit Timah granite massif in Singapore, emphasizing the role of granite weathering in local site effects. A 2.5D geomodel was constructed using geophysical data, boreholes, and geological maps, from which five 2D cross-sections were extracted for dynamic numerical modeling. Simulations were performed to assess resonance frequencies, amplification patterns, peak ground acceleration (PGA), and shear wave velocity (Vs). The dominant frequency ranged between 1.8 and 3.8 Hz, with amplification factors up to 4.5, consistent with HVSR data. The close agreement between HVSR and modeling results highlights the influence of weathered granite layers on site response. A 2D Vs model was derived from the inversion of HVSR and synthetic curves. The findings provide detailed insights into lithological and topographic effects, especially lateral heterogeneities in weathering. This study demonstrates the reliability of numerical modeling for microzonation in granitic terrains and supports its use in enhancing seismic risk assessments and urban planning in weathered rock regions.

Upper-plate aftershocks following megathrust earthquakes are particularly dangerous as they may occur close to densely populated regions. Aftershock numbers decay with time, imposing a time-dependent seismic hazard that is assessed with statistical forecast models. While coseismic static stress transfer cannot explain this time-dependency, transient postseismic deformation due to afterslip, viscoelastic relaxation, and pore-pressure diffusion are potential candidates. Here we demonstrate which postseismic process is the key driver of the upper-plate aftershocks pattern following the 2014 Mw = 8.2 Iquique earthquake in northern Chile. We first use a 4D (space and time) model approach to reproduce the postseismic deformation observed in geodetic data. We then analyze the spatiotemporal stress changes produced by individual postseismic processes and compare them to the upper-plate aftershocks distribution. Our results reveal that stress changes produced by coseismically-induced pore-pressure diffusion best correlate in space and time with increased upper-plate aftershock activity. Moreover, an increase in pore-pressure reduces the three effective principal stress magnitudes likewise. Hence, all faults, regardless of their orientations, are brought closer to failure. This explains the higher diversity of the aftershocks faulting styles. Our findings provide further insights into the link between pore-pressure diffusion and upper-plate deformation in subduction zones and provide grounds for a physics-based aftershock forecast.

ABSTRACT This study provides an updated probabilistic seismic hazard model for Maharashtra state. A new and updated earthquake catalogue including events from January 1600 to October 2021 has been compiled. Six declustering trials using various declustering methods are applied to develop the corresponding six earthquake catalogues. A seventh catalogue (C1) is compiled by extracting common events from these six catalogues. Fault recurrence parameters for linear sources are derived using the parameters estimated from C1. Further, six ground motion prediction equations developed for Peninsular India are initially considered and subsequently reduced to four based on their performance using the global intraplate earthquake ground motion records. Three logic tree models are used which include linear and areal source contributions to estimate peak ground acceleration. Seismic hazard maps are developed for return periods of 2475 and 475 years, evaluating PGA and spectral acceleration at 0.2 and 1.0 s at the bedrock level. Koynanagar and Panvel regions in the western part of the state exhibit higher PGA values for both return periods. The estimated seismic hazard for Area A1 is lower than the values specified by IS (1893) (2016), whereas some areas in A2, A3, and A4 exhibit higher hazard values than those specified in the code.