Source Model and Seismogenic Environment of the Ms 6.4 Yangbi Earthquake in Yunnan, China—Based on InSAR Observation

Abstract

On 21 May 2021, an Ms 6.4 earthquake struck Yangbi County, Dali Prefecture, Yunnan Province, China, which is the largest earthquake to hit this area since 1976. In this paper, we obtained the coseismic deformation of the Yangbi earthquake in Yunnan Province based on the interferometric synthetic aperture radar (InSAR) observation. After that, we obtained the fault geometry and slip distribution model of this earthquake via the two-step inversion method. The maximum deformation in the ascending orbit along the line of sight (LOS) direction was 7.3 cm, and the maximum deformation in the descending orbit along the LOS direction was 8.9 cm; the slip distribution model showed that the slip distribution of this earthquake was concentrated at a depth of 1–14 km, and the maximum slip was 0.6 m at a depth of 5 km. Based on the modeling result, it was inferred that the seismogenic fault of this earthquake was a dextral strike-slip fault on the west side of the Weixi-Qiaohou–Weishan fault. Combining the existing geological data and the changes in Coulomb stress caused by this earthquake, the seismic hazard and seismogenic structure in the area near the epicenter were analyzed and discussed, and the results showed that, in the northwest of the Weixi-Qiaohou fault zone, there will be an increased hazard of a future earthquake in the NW trend; thus, we should pay attention to this area.