New insights into the Menyuan Ms6.9 Earthquake, China: 3D slip inversion and fault modeling based on InSAR remote sensing approach

Abstract

Harnessing high-precision spaceborne InSAR data, this study investigates the seismic impacts of the Ms 6.9 Menyuan earthquake in Qinghai, China, on January 8, 2022. The earthquake occurred at the intersection of the Lenglongling (LLLF) and Tuolaishan (TLSF) faults within the Qilian Haiyuan Fault (QL-HYF) zone, causing extensive infrastructure damage but no fatalities. Previous studies explored the step-over rupture zone and slip distribution of the Menyuan event but often relied on oversimplified rectangular dislocation models, insufficient for capturing complex fault ruptures. This simplification impedes accurate representation of curved fault segments in the QL-HYF zone, leading to unclear slip distribution estimates, particularly at the transition from LLLF strike-slip to TLSF thrust behavior. To address these limitations, this study employs a 3D triangulated angular dislocation slip-inversion approach in an isotropic half-space, enabling precise modeling of curved fault geometries. Leveraging Differential InSAR (D-InSAR) and Pixel Offset Tracking (POT), we reconstructed the earthquake’s 3D displacement field and extracted surface fault traces, informing our angular dislocation model for accurate coseismic slip distribution. Our results revealed significant horizontal displacement, with 38.5 cm of left-lateral movement accompanied by a 4 cm downward thrust. The slip model showed 2.7 m of slip along the LLLF and 0.8 m along the TLSF, concentrated at shallow depths between 2 and 7 km, highlighting surface rupture. The transition zone between the faults acted as a valve, modulating rupture progression and controlling energy release. These findings refine the understanding of coseismic deformation and slip distribution, supporting seismic hazard mitigation and emergency response strategies.