Abstract: Dingri Tibet, occurred a M_W5.7 earthquake On March 20, 2020, locating in the geologically complex intersection of Northern Himalayan fault and Shenzha-Dingjie fault. It is very significant to understand the complex tectonic in this area by studying the source model of this earthquake. In this study, use the Sentinel-1A spaceborne SAR data of ascending and descending orbits, to obtaine the surface deformation field caused by the earthquake by synthetic aperture radar interferometry (InSAR). The maximum surface displacement along the line of sight reaches 0.16 m. Based on the uniform elastic half-space dislocation model and the obtained surface deformation data, we determine the source model including the geometric parameters and the slip distribution of the fault by nonlinear and linear inversion. We also analyze the tectonic characteristics of the seismogenic fault. The results show that the seismogenic fault is a shallow blind normal fault with a small amount of dextral strike-slip component. The fault strike is 319° and the dip angle is 44°. The maximum slip occurred at the depth of 4 km and reached 0.8 m. The seismic moment released by the earthquake is 4.14×10¹⁷ N·m, equivalent to M_W5.7 which is consistent with the seismic waveform inversion results. Finally, we consider that the seismogenic fault of the Dingri M_W5.7 earthquake may be a branch fault belonging to a “Y” shaped structure of the middle part of Shenzha-Dingjie fault. The existence of the “Y” shaped structure may be the reason why many small earthquakes concentrate in this area.

Key words: 2020 Dingri M_W5.7 earthquake, InSAR, Source model