Characterizing the coseismic slip behaviors of earthquakes could offer a better understanding of regional crustal deformation and future seismic potential assessments. On 18 December 2023, an Mw 6.0 earthquake occurred on the Lajishan–Jishishan fault system (LJFS) in the northeastern Tibetan Plateau, causing serious damage and casualties. The seismogenic fault hosting this earthquake is not well constrained, as no surface rupture was identified in the field. To address this issue, in this study, we use Interferometric Synthetic Aperture Radar (InSAR) data to investigate the coseismic surface deformation of this earthquake and invert both ascending and descending line-of-sight observations to probe the seismogenic fault and its slip characteristics. The InSAR observations show up to ~6 cm surface uplift caused by the Jishishan earthquake, which is consistent with the thrust-dominated focal mechanism. A Bayesian-based dislocation modeling indicates that two fault models, with eastern and western dip orientations, could reasonably fit the InSAR observations. By calculating the coseismic Coulomb failure stress changes (∆CFS) induced by both fault models, we find that the east-dipping fault scenario could reasonably explain the aftershock distributions under the framework of stress triggering, while the west-dipping fault scenario produced a negative ∆CFS in the region of dense aftershocks. Integrating regional geological structures, we suggest that the seismogenic fault of the Jishishan earthquake, which strikes NNE with a dip of 56° to the east, may be either the Jishishan western margin fault or a secondary buried branch. The optimal finite-fault slip modeling shows that the coseismic slip was dominated by reverse slip and confined to a depth range between ~5 and 15 km. The released seismic moment is 1.61 × 10¹⁸ N·m, which is equivalent to an Mw 6.07 earthquake. While the Jishishan earthquake ruptured a fault segment of approximately 20 km, it only released a small part of the seismic moment that was accumulated along the 220 km long Lajishan–Jishishan fault system. The remaining segments of the Lajishan–Jishishan fault system still have the capability to generate moderate-to-large earthquakes in the future.

Between January and April 2022, three moderate earthquakes (Mw 5.6 on 23 January, Mw 5.7 on 25 March, and Mw 5.1 on 15 April) struck the Hala Lake area of Delingha, Qinghai, China. Their seismogenic faults are poorly mapped, resulting in an unclear understanding of their kinematics and regional seismotectonics. In this study, we employed Interferometric Synthetic Aperture Radar (InSAR) observations to reconstruct the coseismic deformation fields of the Mw 5.6 and 5.7 events. We then utilized a Bayesian inversion algorithm to delineate the fault geometries of the two events, and further resolved their coseismic fault slip. Our results reveal that these earthquakes ruptured different fault planes: the fault plane of the Mw 5.6 event dips westward at an angle of 60°, while the Mw 5.7 event ruptured as a nearly vertical fault with a dipping angle of 89°. The finite-fault slip inversions further demonstrate that the coseismic rupture of the Mw 5.6 event was predominantly concentrated between depths of 2 km and 7 km, with a maximum slip of 0.18 m; in contrast, the Mw 5.7 event was mainly concentrated between depths of 2 km and 9 km, with a maximum slip of 0.4 m. We calculated the coseismic Coulomb failure stress change (ΔCFS) induced by these two earthquakes. Integrating the analysis of ΔCFS and the spatial distribution of aftershocks, we argue that the sequence earthquakes were triggered by the proceeding earthquakes.