Coseismic Deformation, Fault Slip Distribution, and Stress Changes of the 2025 MS 6.8 Dingri Earthquake from Sentinel-1A InSAR Observations

On 7 January 2025, a MS 6.8 earthquake struck Dingri County, southern Tibet, within the extensional regime of the central Himalaya–southern Tibetan Plateau. Using ascending and descending Sentinel-1A SAR data, we applied a two-pass Differential InSAR (D-InSAR) approach with SRTM DEM data to retrieve high-precision coseismic deformation fields. We observed significant LOS deformation, revealing peak displacements of −1.06 m and +0.76 m, with deformation concentrated along the Denmo Co graben and clear offsets along its western boundary fault. Nonlinear inversion using the Okada elastic dislocation model and a quadtree down-sampled dataset yields a rupture plane 28.42 km long and 12.81 km wide, striking 183.51°, dipping 55.41°, and raking −71.95°, consistent with a predominantly normal-faulting mechanism with a minor left-lateral component. Distributed-slip inversion reveals that peak slip (4.79 m) was concentrated in the upper ~10 km of the fault, with the main asperity located in the central fault segment. The seismic moment is estimated to be 4.24 × 1019 Nm, which corresponds to a magnitude of MW 7.05. Coulomb failure stress (ΔCFS) calculations indicate stress increases (>0.01 MPa) at the northern and southern rupture terminations (5–10 km depth) and the flanks at 15–20 km depth, suggesting elevated seismic potential in these regions. This integrated InSAR–modeling–stress analysis provides new constraints on the source parameters, slip distribution, and tectonic implications of the 2025 Dingri earthquake, offering important insights for regional seismic hazard assessment.