Postseismic surface deformation offers key insights into subsurface lithospheric rheology and earthquake fault behavior, yet geodetic data often fail to capture its full complexity. Here, we use satellite radar images to derive time series of three-dimensional surface displacements following the 2023 Kahramanmaraş (Türkiye) earthquakes. The results show strong spatial and temporal deformation asymmetry across the East Anatolian Fault with the stiffer Arabian lithosphere exhibiting slower deformation decay than the Anatolian side. The temporal asymmetry excludes elastic afterslip from being the main postseismic process and instead the postseismic response is dominated by asymmetric viscoelastic relaxation as well as poroelastic rebound. These findings underscore the importance of both temporal and three-dimensional spatial deformation data in advancing understanding of post-earthquake recovery processes and subsurface lithospheric structure.

Optical images acquired by satellite are widely used to measure the displacement field caused by earthquakes co-seismic ruptures both in the near and the far field. So far, this technique relies mostly on image correlation to locate pixels from an image acquired before the event on another acquired after. However, such approach suffers from several limitations inherent in the correlation method used, such as the need for sufficient texture to make objects « recognizable » from one image to the other, or limited changes in the landscape over time, for the same reason. These limitations can lead to noisy results and even prevent any measurement from being made.To overcome such limitations, machine learning can be used instead of correlation to train a model to compute displacement maps from a pair of images. Steady and significant progress have been made in machine learning technics, and especially for image processing and computer vision, in recent years, and they need to be adapted to our case study. First, a training dataset is carefully designed, to enable the network to learn how to measure pixel displacements in satellite images, with sub-pixel accuracy, in the most realistic way possible. Since no ground truth is available, we build synthetic examples, where a realistic and known deformation is applied to one of the images in a pair of 10-m-resolution Sentinel-2 satellite images, which originally contains no displacement. This realistic synthetic dataset is then used to feed a model.Our network is capable of estimating a displacement field from images whose resolution differs signifiantly from that of the training dataset (for example, from a 0.5-m-resolution Pléiades image pair) and achieves results comparable to those of state-of-the-art methods, with even finer details, at both pixel and sub-pixel resolution levels. However, the ability of machine learning to overcome limitations due to landscape changes caused by time remains to be proven.

Why do some earthquakes repeatedly rupture discrete fault segments, while others rupture entirefaults? Answering this remains fundamental to improving seismic hazard analysis and, in turn, tohazard preparedness and mitigation efforts. Over the past two decades, several mechanisms forrupture termination and propagation have been proposed, including variation in geometric,structural, and geologic characteristics of faults (Aki, 1979; King and Nabelek, 1985). In this studywe investigated the Eastern Precordillera (EPC) of the Andes Mountain in Argentina which isclassified into three segments: Villicum, Las Tapias, and Zonda–Pedernal (Siame et al., 2002) todetermine whether the historical surface ruptures associated with major earthquakes crossed thesegment boundaries, or whether rupture propagation was arrested by structural asperitiesindicating an asperity-controlled behavior. To address this, we conducted a new paleoseismicinvestigation at this site to complement and integrated with the preexisting dataset to evaluate theextent of past surface ruptures in relation to fault geometry and structural segmentation. We havecomplied earthquake timing of six earthquakes. Preliminary results suggest that, of the sixidentified events, only one earthquake appears to have ruptured across an ~18 km-long segmentgap, including a ~4 km stepover and notable lithologic variation evidence consistent with a multi-segment rupture event.

Accurate measurements of coseismic slip distributions derived from geomorphic markers provide essential insights into earthquake rupture dynamics and make a significant contribution to seismic hazard evaluation. With the increased availability of high-resolution topographic data and advanced statistical techniques such as cumulative offset probability distribution (COPD), reconstructing single-event coseismic displacement from cumulative offsets of successive paleoearthquakes has become more feasible. However, assessing the reliability of these methods remains critical. The 1920 Mw7.9 Haiyuan earthquake, the most recent major event along the strike-slip Haiyuan fault, serves as an ideal case study due to notable discrepancies in previously reported displacement measurements. In this study, we utilize very high-resolution (0.1 m) topographic data derived from aerial imagery processed via the Structure from Motion (SfM) technique, covering approximately 85 km of the similar to 240 km rupture length. Our analysis, based on detailed horizontal slip measurements and COPD calculation, yields a maximum displacement of 7.6 +/- 0.8 m for the 1920 Haiyuan earthquake, differing from previous estimates but aligning well with global scaling relationships for strike-slip earthquakes. Our results reveal three COPD peaks in the geomorphic records along the Haiyuan fault. The displacement interval between the two most recent peaks is similar to that of the latest peak, with reduced displacement observed in the western section. These findings suggest that previous interpretations of four to five events may significantly overestimate single-event slip. Comparisons with previous studies underscore the methodological challenges in COPD-based reconstructions, including uncertainties from different slip measurement methods, geomorphic marker interpretations, fault geometry, along-strike slip variability, and the contribution of moderate-magnitude earthquakes to cumulative offsets.

The Aceh Fault, a major strike-slip fault forming the northernmost segment of Great Sumatran Fault, exhibits recent faulting through prominent scarps along its 250-km length. Running northwest-southeast, it traverses northwestern Sumatra from Tripa to Banda Aceh, a city of over 268,000 residents that is more commonly associated with the 2004 tsunami, but also lies directly on this active fault zone. Understanding the earthquake rupture history, including pre-instrumental events, is essential to characterize long-term seismic patterns and to assess associated hazards. We investigated the fault using 8-m resolution DEM (DEMNAS) for the entire fault zone, 15-cm resolution lidar DEM for selected areas, field mapping, and paleoseismology. Two paleoseismic trenches excavated in the Geumpang area reveal evidence of at least three ground-rupturing earthquakes over the past similar to 1000 years. Event timing was constrained by radiocarbon analysis of detrital charcoal, providing sufficient chronological control to identify two well-dated events and one older event with lower precision. These results confirm that the Aceh Fault is active, delineate its surface trace, and offer the first detailed record of prehistoric earthquakes along this fault. This information contributes to improved seismic hazard mapping and a clearer understanding of tectonic risk in the Banda Aceh region.

Burning histories derived from charcoal preserved in sediment archives offer scope to reconstruct past climate and landscape dynamics. The fault-bounded Aksay Pond in northwestern China preserves an 80-year sediment sequence spanning 1931 to 2012 that reveals undetected punctuated fire events within the last ca. 1000 years. We used Bayesian inferential modelling of 24 macrocharcoals that have been directly 14C Accelerated Mass Spectrometry dated to examine past phases of fire activity and compare these phases with other fire-proxy records from the Altai Ranges. That these charcoals formed, were stored in the landscape and subsequently mobilised into the pond suggests that fires occurred at these different times. This method for examining fire histories differs from more traditional techniques and has some inherent uncertainties that are discussed. Importantly, our charcoal record does not attempt to infer severity, intensity or number of fires but identifies undetected periods of burning. Charcoal was dated to three statistically distinct phases spanning 95% highest posterior density ranges of 1170 to 1290 CE (Phase 3), 1410 to 1650 CE (Phase 2) and 1720 to 1900 CE (Phase 1) with some post-1950 CE charcoal. Bayesian modelling also demonstrates that Phase 3 does not coincide with burning histories from elsewhere in the Altai Ranges suggesting localised fires during the early to middle stages of the Medieval Climate Anomaly. Phase 2 charcoals overlap with a significant period of burning from the western Altai Range during the early stages of the Little Ice Age (LIA) indicating a larger regional environment primed for fire. Phase 3 charcoals from Aksay Pond occurs during the transition from peak LIA to Recent Warming and likely reflects regional increases in anthropogenic burning. Our Bayesian analysis of the burning periods from the Aksay Pond with other fire records from the Altai Ranges demonstrates that burning in the region is spatio-temporally heterogeneous and that further sites need investigating to capture the true history of burning from the region. Our novel approach also demonstrates the utility of short-lived sedimentary archives as alternative proxy sources for long-term fire histories in data-scarce regions.

The Gulf of Aqaba (GoA) is the seismically most active region in the Red Sea, with a history of large earthquakes and posing a high seismic hazard to coastal communities. This study uses back‐projection and dynamic rupture simulation to investigate the largest instrumentally recorded earthquake in the GoA, the 1995 7.2 Nuweiba earthquake, to understand stress loading, failure mechanisms, and cascading rupture potential on complex multi‐segment fault systems. Our results reveal a multi‐segment cascading rupture with supershear rupture on the optimally prestressed Aragonese Fault. Supershear rupture significantly amplified offshore ground shaking, elevating seismic hazard for the narrow gulf's coastal regions. This event partially ruptured the GoA fault system, increasing Coulomb stress on the unbroken southern Arnona Fault, which has been silent since 1588. This stress loading likely advanced a future rupture on this critical segment, requiring close monitoring and increased preparedness for a potential large earthquake in the region.

Shallow creep along strike‐slip faults is essential in releasing strain during earthquake cycles. However, its origin—whether inherent or triggered by earthquakes—remains debated. Using Interferometric Synthetic Aperture Radar phase‐gradient data, we map shear‐strain rates along the East Anatolian Fault Zone (EAFZ) before and after the 2020 Mw6.8 Elazığ and 2023 Mw7.8/Mw7.6 Kahramanmaraş earthquakes. The observed strain‐rate distributions strongly correlate with coseismic slips in the EAFZ. The stress‐driven afterslip model constrained by the phase‐gradient time series reproduces distinct decaying patterns of newly activated creeping segments, showing that rapid afterslip may decay slowly and keep slipping for decades. Our results reveal that large earthquakes can accelerate, expand, and trigger shallow fault creep, highlighting the roles of fault frictional properties and stress changes caused by nearby earthquakes. These findings provide new insights into fault creep mechanisms and their linkage to large earthquakes, with implications for faulting behaviors.

The Mw 7.7 Ekinozu Earthquake is the second shock of the devastating 2023 Kahramanmaraş earthquake doublet. It ruptured bilaterally along a ~150 km-long stretch of the Cardak-Surgu fault. Along its eastern section, instead of propagating along the Surgu fault to connect with the main East Anatolian Fault where the Mw7.8 shock occurred, the rupture unexpectedly turned to the northeast to propagate along a secondary structure. Surface ruptures and assessment of displacement along that section of the fault have been challenging to map, and these are less documented. This is crucial for unraveling the entire rupture process, fault growth, and related seismic hazards. In this study, we focus on the eastern end of the ~57-km long surface rupture caused by the Mw 7.7 Ekinozu Earthquake. By correlating high-resolution optical images SPOT (pre-earthquakes, resolution 1.5m) and Pléiades (post-earthquakes, resolution 50 cm), we computed displacement maps at 1.5 m ground resolution for the study area. In addition, using the post-event Pleiades images, we meticulously characterized the coseismic surface ruptures in detail. Our mapping presents a segmented surface rupture trace with azimuth variations and several distinguishably complex geometries, such as double bends and branches. Furthermore, our investigation includes precise measurements of on- and off-fault surface displacement with sub-pixel detection over the ~57-km long section. Our findings underscore the significance of detailed interpretations of coseismic surface rupture and coseismic displacement measurements in comprehending the propagation of the seismic rupture.

The Aceh Fault, part of Indonesia's Great Sumatran Fault System, exhibits recent faulting through prominent scarps along its 250-kilometer length. Running northwest-southeast, it spans northwestern Sumatra from Tripa to Banda Aceh, a city of over 268,000 residents. Understanding the complete faulting history is essential for assessing seismic risk, as instrumental records are too recent to capture long-term patterns. We study the fault by combining remote sensing using 8-m resolution DEM (DEMNAS) for the entire area and 15-cm resolution (LiDAR drone survey) for selected areas, field methods, and paleoseismology. We excavated two paleoseismic trenches across the fault and documented evidence of at least three well-dated ground-rupturing earthquakes from the upper 2 meters of strata spanning the last ~1000 years. The event chronology is constrained by 15 radiocarbon dates on detrital charchoal. This new paleoseismic data confirms that the Aceh Fault is active. Our study delineates the active trace of the fault zone and provides the first detailed information about significant prehistoric earthquakes along this fault. These findings improve seismic hazard maps and enhance understanding of the region's seismic risks.

Abstract Quantifying coseismic fault offsets for surface ruptures of major earthquakes is important for earthquake cycle and slip-rate studies, and thus for earthquake hazard assessments. However, measurements of such offsets generally underestimate fault slip due to inelastic deformation and secondary fault offsets, i.e., off-fault damage. Here, we use satellite synthetic aperture radar images to quantify off-fault damage in the two 2023 Kahramanmaraş (Türkiye) magnitude 7.8 and 7.6 earthquakes. We first derive three-dimensional coseismic surface displacements and show that on average ~35% of the coseismic slip is accommodated by off-fault damage within 5–7 km of the coseismic surface ruptures. Fault sections exhibiting geometrical complexities (e.g., bends and step-overs) experienced a higher level of off-fault damage than simpler fault sections. Our results highlight the importance of extending off-fault damage assessments to several km away from fault ruptures and indicate that fault offset measurements may underestimate slip-rate estimations by as much as a third.

Fault maturity has been proposed to exert a first-order control on earthquake rupture, yet direct observations linking individual rupture to long-term fault growth are rare. The 2021 Mw 7.4 Maduo earthquake ruptured the east-growing end of the slow-moving (~1 mm/yr) Jiangcuo fault in north Tibet, providing an opportunity to examine the relation between rupture characteristics and fault structure. Here, we combine field and multiple remote sensing techniques to map the surface rupture at cm-resolution and document comprehensively on-fault offsets and off-fault deformation. The 158 km-long surface rupture consists of misoriented structurally inherited N110°-striking segments and younger optimally oriented N093°-striking segments, relative to the regional stress field. Despite being comparatively newly formed, the ~N093°-striking fault segments accommodate more localized strain, with up to 3 m on-fault left-lateral slip and 25-50% off-fault deformation, and possibly faster rupture speed. These results are in contrast with previous findings showing more localized strain and faster rupture speed on more mature fault segments; instead, our observations suggest that fault orientation with respect to the regional stress can exert a more important control than fault maturity on coseismic rupture behaviors when both factors are at play.

The Alpine-Himalayan belt is one of Earth's most dynamic and complex regions, characterized by intense tectonic deformation and seismicity. Comprehensive analyses of continental-scale crustal deformation and seismic hazards along this extensive orogenic belt require the compilation of large geodetic data sets. In this study, we integrate 42 published Global Navigation Satellite System (GNSS) velocity fields, building an internally consistent data set for the entire belt, spanning from Iberia to Southeast Asia and comprising 11,177 horizontal and 3,940 vertical velocities. We use this unified GNSS velocity field to estimate surface strain rates and their posterior uncertainties in the eastern Mediterranean region and the India-Asia collision zone. Our results show large-scale agreement between the orientation and style of geodetic and seismic strain rate tensors across the belt. Additionally, our analyses substantiate previously documented azimuthal alignments between principal strain rate directions and seismic anisotropy orientations, often used as a proxy for finite strain in the convecting mantle. These correlations are particularly apparent in the Aegean, North Anatolia, Tibet, Tian Shan, Altai, Sayan, and Baikal regions, underscoring the need for future research on the relationship between mantle flow and lithospheric deformation.

Mountains in collisional orogens generally grow as crustal rocks are advected over low-angle thrust faults, suggesting a close relationship between tectonic uplift and upper crustal shortening. For example, the Himalayas, hosting large-scale thrust fault systems, undergoes similar to 15-20 mm/year shortening and concomitant similar to 5 mm/year active uplift. However, geodetic observations reveal an active uplift of 1-2 mm/year across the East Kunlun Shan mountain range, the northern margin of the Tibetan Plateau, where no active thrust fault has been identified. This active uplift is too fast to be explained by the limited horizontal shortening of at most 1.0 +/- 0.2 mm/year. After quantifying and correcting for contributions arising from erosion, (de)glaciation, and recent earthquakes, the uplift rate across the East Kunlun Shan still amounts to 1.0 +/- 0.5 mm/year. Our simulations show that mantle processes cannot explain the GPS-observed uplift. We find that lower crustal thickening, rather than upper crustal shortening alone, drives the ongoing uplift across the East Kunlun Shan, hence challenging our current views on mountain range dynamics.

Seismic gaps are fault sections that have not hosted a large earthquake for a long time compared to neighbouring segments, making them likely sites for future large events. The 2025 Mw 7.7 Mandalay (Myanmar) earthquake, on the central section of the Sagaing Fault, ruptured through a known seismic gap and ~160 km beyond it, resulting in an exceptionally long rupture of ~460 km. Here we investigate the rupture process of this event and the factors that enabled it to breach the seismic gap by integrating satellite synthetic aperture radar observations, seismic waveform back-projection, Bayesian finite-fault inversion and dynamic rupture simulations. We identify a two-stage earthquake rupture comprising initial bilateral subshear propagation for ~20 s followed by unilateral supershear rupture for ~70 s. Simulation-based sensitivity tests suggest that the seismic gap boundary was not a strong mechanical barrier in terms of frictional strength, and that nucleation of the earthquake far from the gap boundary, rather than its supershear speed, allowed the rupture to outgrow the gap and propagate far beyond it. Hence, we conclude that the dimension of seismic gaps may not reflect the magnitude of future earthquakes. Instead, ruptures may cascade through multiple fault sections to generate larger and potentially more damaging events. The 2025 Mw 7.7 Mandalay earthquake in Myanmar breached and propagated beyond a long-quiescent segment owing to a mechanically weak barrier at the segment boundary and distant nucleation, according to seismic, geodetic and numerical analyses.

We present preliminary results from a paleoseismic study of the middle branch of the Northern Anatolian Fault (MNAF) in Turkey. Despite low instrumental seismicity and geodetic slip rates (~2.5 mm/yr) relative to the northern branch, historical, archeological, and paleoseismic studies indicate the MNAF has hosted several damaging earthquakes in the last two millennia. Recent geomorphic and bathymetric analyses reveal segmentation of the MNAF that may indicate strain partitioning of normal and strike slip along parallel fault strands. However, it remains uncertain whether these fault segments have ruptured simultaneously. Geologic studies have constrained right-lateral slip rates to between 2 and 5.3 mm/yr, with most results contrasting against the present-day geodetic slip rate of ~2.5 mm/yr. Whether this represents a reduction in strain rate along this branch of the Northern Anatolian fault is not clear. Our study has two main objectives: first, to delineate the earthquake history along the newly identified segment of the MNAF beneath Lake Iznik and map its onshore extensions to the east and west of the lake; second, to determine the right-lateral slip rate of the MNAF across different temporal scales. We will present preliminary results from geomorphic mapping, electromagnetic conductivity and ground penetrating radar surveys, and paleoseismic trenching aimed at achieving these objectives. By further establishing the earthquake history and length of the new branch beneath Lake Iznik, we aim to ascertain whether this segment has ruptured concurrently with parallel and along-strike segments, allowing us to estimate paleo-earthquake magnitudes and maximum rupture lengths. Concurrently, by constraining the slip rate of the MNAF over time, we seek to understand whether slip along this branch has decreased and if this reduction is linked to a subsequent increase in slip rate on either the northern or southern branch of the Northern Anatolian Fault.

Knowing about the geometry of both (i) ruptured zones during seismic events, and (ii) faults throughout seismic cycles, as well as the evolution of this geometry, is important to understand what is controlling the start and the ending of large earthquakes. In this study, we use 3D Discrete Element Modeling (DEM) in order to simulate a strike-slip fault, formed from an initially homogeneous, intact medium representing brittle rock that is submitted to tectonic loading. Indeed, this numerical method models the crust as an assembly of rigid spheres which are linked by user-defined interactions and reconfigurate very naturally when subjected to loading. Therefore, such approach is adapted to study the evolution of fault geometry through earthquake cycles, since it permits to simulate large displacements of the particles, while avoiding prescribing fault location and geometry, and letting such geometry evolve freely. A 3D parallelepipedic model is designed and then indefinitely sheared by assigning periodic boundary conditions. The particular feature of our model is the implementation of a healing phenomenon, a key process which allows fractured zones to restrengthen after a slip event. During the simulation, the position of particles and the state of their bonds are recorded at regular time intervals; consequently, the shape and dimension of deformation are evaluated, the evolution of fault geometry is monitored, and the stresses in the domain can be measured. Results show a stick-slip behaviour which can be identified as earthquakes separated by locking periods. In addition, the amount of displacement and the rupture surface can be estimated and enable the computation of a magnitude-like quantity. Thus, earthquake-like events seem to follow a magnitude-frequency relationship, and earthquake-like surface deformations are comparable to observations of ground deformation after real size earthquakes. Eventually, the evolution of the fault geometry during the simulation is also scrutinized.

Integration of paleoseismic data from multiple sites is important to assess the past fault rupture scenarios and determine an earthquake chronology for the entire fault system. However, the current methods used to combine paleoseismic data are diverse and lack theoretical foundations from a mathematical perspective. We present a method to evaluate and integrate paleoseismic event data from multiple sites into a single earthquake time history. We apply this method to the central-eastern fault sections of the Altyn Tagh Fault using data from ten fault trenches. Applying a Bayesian approach we constructed time-stratigraphic models that yield the probability density functions corresponding to the age of individual earthquakes at each site. Then, our method to integrate these data consists of two main steps: 1) we constructed a rupture pool with all the modeled event ages, and we evaluated the overlapping degree between the site PDFs; 2) For sufficiently contemporary PDFs we combine them by computing the weighted-mean method which emphasizes the overlap in the site earthquake times. The weighted-mean method yields smaller earthquake-time uncertainties compared to the rupture-mean approach and is consistent with the earthquake rupture assumptions behind the integration of paleoseismic data and the probability theory of density functions. This approach helps to clarify the timing and rupture extent of past earthquakes along central-eastern ATF and is essential to improve the earthquake probability assessment for the region.