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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. [ABSTRACT FROM AUTHOR]

Objectives: On January 8th 2022, an Ms 6.9 earthquake struck Menyuan, Qinghai Province, China. The epicenter is located in the middle section of Qilian-Haiyuan fault in the northeast margin of the Tibetan Plateau, which is a seismic gap. It is of great significance to study this earthquake for under-standing the tectonic deformation mechanism, strain release process and seismic hazards of the NE Tibetan Plateau.Methods: Differential synthetic aperture radar interferometry (D-InSAR) is used to obtain the coseismic deformation along the line of sight (LOS) of the Menyuan earthquake from Sentinel-1 satellite images. The co-registration of optically sensed images and correlation are used to obtain the EW coseismic deformation from the multi-temporal Sentinel-2 data. Based on the coseismic deformation field derived from InSAR interferograms, we invert the slip distribution. Results: The LOS deformation fields showed that the Menyuan earthquake caused a surface rupture of about 20 km long and the maximum LOS displacement was 0.75 m. The maximum EW displacement derived from optical images was 2.5 m. The slip distribution model showed that the Menyuan earthquake was dominated by a sinistral strike-slip. The coseismic slip is concentrated at a depth of 0 - 10 km. The maximum slip was 3.25 m at a depth of 4.89 km and the rake angle was 10.44°. The estimated total seismic moment is 1.07x1019 N.m, corresponding to a magnitude of Mw 6.6. Conclusions: According to the results from aftershock relocation, field investigation and tectonic background, we infer that the seismogenic fault is the Lenglongling fault and the eastern segment of Tuolaishan fault is also ruptured. The stress on the eastern segment of the Lenglongling fault and the western segment of the Tuolaishan fault is enhanced, implying that there is the possibility of strong earthquakes in this region in the future. [ABSTRACT FROM AUTHOR]