Seismic Source Complexities Revealed by InSAR and Analytical Modeling: The 2025 Mw 7.1 Dingri Earthquake

This study investigates the Mw 7.1 earthquake that struck the Southern Tibetan Plateau (Xizang) on 7 January 2025, using joint Interferometric Synthetic Aperture Radar (InSAR) observations and inverse modeling to characterize the fault geometry and slip distribution. Coseismic interferograms derived from Sentinel-1 and ALOS-2 data reveal complex surface deformation patterns, indicating rupture along four distinct fault segments. This configuration provides a more detailed fault segmentation than proposed in previous studies, featuring predominantly normal faulting on a north–south-trending structure consistent with regional extensional tectonics. Integrated analysis of coseismic deformation, source modeling, and Coulomb Failure Function (ΔCFF) stress changes suggests that the three secondary fault segments were potentially activated synchronously with the mainshock, in addition to the principal rupture. The results underscore the complexity of the seismic source and document the activation of an antithetic fault segment, for which the InSAR observations provide compelling quantitative evidence.