Rupture Process and Seismogenic Mechanism of the 2023 Mw 6.0 Jishishan Earthquake: Insights from Joint Inversion of InSAR, GNSS, and Tele-Waveforms

On 18 December 2023, an Mw 6.0 earthquake struck Jishishan County, Gansu Province, China, rupturing a segment of the Lajishan fault system along the northeastern margin of the Tibetan plateau. To characterize the seismogenic fault geometry and the spatiotemporal evolution of the rupture, we developed a joint inversion framework that integrates Interferometric Synthetic Aperture Radar (InSAR), Global Navigation Satellite System (GNSS) coseismic displacements, and far-field seismic waveforms. The fault geometry was constrained through a nonlinear inversion based on coseismic InSAR deformation. Using the optimal fault geometry, we performed a kinematic finite-fault inversion that jointly incorporates InSAR line-of-sight displacements, static GNSS offsets, and seismic waveforms to resolve the rupture process. Our results show that the rupture was mainly concentrated at depths of 5–12 km, with a maximum slip of ∼30 cm. The estimated seismic moment is 1.0×1018 N·m, corresponding to Mw 5.94. The total rupture duration is ∼20 s. Regional interseismic GNSS velocities and strain-rate fields indicate that the event occurred within a compressional tectonic regime and was dominated by thrust faulting with a minor strike-slip component, providing insights into tectonic loading and seismogenesis within the Lajishan fault system. Coulomb stress calculations further suggest that stress transfer from the mainshock may have contributed to the subsequent aftershock activity. Our results provide constraints on the rupture behavior and tectonic loading of the Lajishan fault system and improve our understanding of seismogenesis along the northeastern margin of the Tibetan plateau, with implications for regional seismic hazard assessment.