Coseismic deformation and stress triggering of the 2021 MS6.4 Yangbi earthquake inverted from integrating GNSS and InSAR displacement fields

Abstract

On 21 May 2021, the MS6.4 Yangbi earthquake occurred at the Tibetan Plateau’s southeastern margin along the Weixi-Qiaohou-Weishan fault. We obtained the fine coseismic deformation fields by integrating 37 near-field GNSS observations and Sentinel-1 InSAR observations of the ascending and descending orbits. Considering that the earthquake did not rupture to the surface, the existing earth fault data is difficult to effectively constrain the deep underground fault. We used aftershock precision location data to constrain fault strike, dip angle, and depth, effectively integrate GNSS and InSAR data, and obtained the fault model closest to the real fault. Based on the coseismic slip distribution model, we calculated the Coulomb stress generated from the earthquake and discussed the triggering relationship between the change of coseismic Coulomb stress and the aftershock distribution. The results show that the maximum rupture occurred at the southeast side of the epicenter and the overall unilateral rupture characteristic. We calculated the stress change when the Yangbi earthquake ruptured, significantly reducing the stress difference between the fault and the surrounding area, which has a significant unloading effect on the surrounding faults and reduces the seismic risk of the surrounding faults.