Summary. We investigate the slip distribution of the 2008 May 12 Wenchuan Ms 7.9 earthquake using GPS data and InSAR measurements under a linear inversion sche

Investigating relationships between temporally- and spatially-related continental earthquakes is important for a better understanding of the crustal deformation, the mechanism of earthquake nucleation and occurrence, and the triggering effect between earthquakes. Here we utilize Global Positioning System (GPS) velocities before and after the 2008 Mw 7.9 Wenchuan earthquake to invert the fault coupling of the Longmenshan Fault (LMSF) and investigate the impact of the 2008 Mw 7.9 Wenchuan earthquake on the 2013 Mw 6.6 Lushan earthquake. The results indicate that, before the 2008 Mw 7.9 Wenchuan earthquake, fault segments were strongly coupled and locked at a depth of ~18 km along the central and northern LMSF. The seismic gap between the two earthquake rupture zones was only locked at a depth < 5 km. The southern LMSF was coupled at a depth of ~10 km. However, regions around the hypocenter of the 2013 Mw 6.6 Lushan earthquake were not coupled, with an average coupling coefficient ~0.3. After the 2008 Mw 7.9 Wenchuan earthquake, the central and northern LMSF, including part of the seismic gap, were decoupled, with an average coupling coefficient smaller than 0.2. The southern LMSF, however, was coupled to ~20 km depth. Regions around the hypocenter of the 2013 Mw 6.6 Lushan earthquake were also coupled. Moreover, by interpreting changes of the GPS velocities before and after the 2008 Mw 7.9 Wenchuan earthquake, we find that the upper crust of the eastern Tibet (i.e., the Bayan Har block), which was driven by the postseismic relaxation of the 2008 Mw 7.9 Wenchuan earthquake, thrust at an accelerating pace to the Sichuan block and result in enhanced compression and shear stress on the LMSF. Consequently, downdip coupling of the fault, together with the rapid accumulation of the elastic strain, lead to the occurrence of the 2013 Mw 6.6 Lushan earthquake. Finally, the quantity analysis on the seismic moment accumulated and released along the southern LMSF show that the 2013 Mw 6.6 Lushan earthquake should be defined as a “delayed” aftershock of the 2008 Mw 7.9 Wenchuan earthquake. The seismic risk is low along the seismic gap, but high on the unruptured southwesternmost area of the 2013 Mw 6.6 Lushan earthquake.

On February 6, 2023, an Mw 7.9 earthquake occurred in the western section of the East Anatolia Fault Zone (EAFZ). It was subsequently followed by an Mw 7.7 earthquake on the northern branch of the EAFZ, known as the Sürgü Fault Zone. Coseismic deformation fields were derived for these earthquakes using joint evaluation of near-field strong motion data, Global Navigation Satellite System data, and Synthetic Aperture Radar datasets. The coseismic slip distribution model was determined through the joint kinematic finite fault inversion. The Mw 7.9 earthquake was a left-lateral strike-slip event, predominantly occurring at depths up to 20 km. The earthquake displayed three distinct asperities that correlate well with bends and stepovers along the EAFZ. The Mw 7.7 earthquake also exhibited left-lateral strike-slip characteristics, with a major asperity along the Çardak Fault featuring a maximum slip of approximately 9.5 m at depths between 0 and 24 km. The occurrence of this unanticipated large Mw 7.9 catastrophic seismic event on a fault with low-intermediate structural maturity is noteworthy. In the vicinity of immature faults with multiple jogs, stress tends to accumulate at barrier locations. When the accumulated stress near several adjacent barriers reaches a certain threshold, it may result in the transformation of multiple barriers into asperities, triggering cascading ruptures.

The Mw 7.0 Dingri earthquake, which occurred on 7 January 2025, occurred at the southern end of the Xainza-Dinggyê Fault Zone within the South Tibet Rift (STR) system, in the Dengmecuo graben. It is the largest normal-faulting event in the region recorded by modern instruments. Using Sentinel-1A and Lutan SAR data combined with strong-motion records, we derived the coseismic surface deformation and slip distribution. InSAR interferograms and displacement vectors confirm a typical normal-faulting pattern. The slip model, based on an elastic half-space assumption, identifies the Dengmecuo Fault as the source fault, with an average strike of ~187° and a dip of ~55°. The rupture was concentrated within the upper 10 km, with a maximum slip of 4–5 m at ~5 km depth, extending to the surface with ~3 m vertical displacement. Partial rupture (≤2 m) in the southern segment (5–10 km depth) did not reach the surface, likely due to lacustrine deposits or possible post-seismic stress release. The rupture bottom intersects the fault plane of the South Tibet Detachment System (STDS), suggesting a restraining effect on coseismic rupture propagation. Considering stress transfer along the Main Himalayan Thrust (MHT), we propose that the 2025 Dingri earthquake is closely associated with stress transfer following the 2015 Gorkha earthquake in the lower Himalayas.

The 12 November 2017 Darbandikhan earthquake (Mw 7.3) occurred along the converence zone. Despite the extensive research on this earthquake, none of this work explained whether this earthquake rupture was limited to the thick sedimentary cover or it extends to the underlying crystalline basement rock (or both). Besides, whether this region will generate devastating earthquakes again and whether there is a one-to-one correlation between these anticlines and blind-reverse faults need further investigation. In this study, we derived the co-seismic interferograms from the Sentinel-1A/B data and successfully described the surface deformation of the main seismic zone. The fringe patterns of both the ascending and descending interferograms show that the co-seismic deformation is dominated by horizontal movements. Then, using the along- and across-track deformation fields of different orbits, we retrieved the three-dimensional deformation field, which suggests that the Darbandikhan earthquake may be a blind thrust fault close to the north–south direction. Finally, we inverted the geometrical parameters of the seismogenic fault and the slip distribution of the fault plane. The results show that the source fault has an average strike of 355.5° and a northeast dip angle of −17.5°. In addition, the Darbandikhan earthquake has an average rake of 135.5°, with the maximum slip of 4.5 m at 14.5 km depth. On the basis of the derived depth and the aftershock information provided by the Iranian Seismological Center, we inferred that this event primarily ruptured within the crystalline basement and the seismogenic fault is the Zagros Mountain Front Fault (MFF). The seismogenic region has both relatively low historical seismicity and convergent strain rate, which suggests that the vicinity of the epicenter may have absorbed the majority of the energy released by the convergence between the Arabian and the Eurasian plates and may generate Mw > 7 earthquakes again. Moreover, the Zagros front fold between the Lurestan Arc and the Kirkuk Embayment may be generated by the long-distance slippage of the uppermost sedimentary cover in response to the sudden shortening of the MFF basement. We thus conclude that the master blind thrust may control the generation of the Zagros front folding.