Abstract: In this study, the coseismic deformation filed of the 2015 Pishan M_W6.4 earthquake is obtained using Sentinel-1A satellite data, the coseismic deformation filed shows an uplift on the north of the epicenter and subsidence in the south along the light of sight. The maximum uplift is 12.9 cm and the maximum subsidence is 5.5 cm. With the InSAR deformation measurements in the light of sight direction, we focused on the nonlinear inversion of the seismic fault geometry models by the Multipeaks Particle Swarm Optimization (MPSO) and Monte Carlo (MC) algorithms. Combining fault model parameters from the MC inversion algorithm and GPS coseismic deformation data the fault slip distributions were retrieved by the Steepest Descent Method (SDM). The comprehensive analysis of the results shows that the seismogenic fault of Pishan earthquake should be a hidden fault with the length is 48 km, the width is 35 km, the strike angle is 111°, the rake angle is 19°, the average rake angel is 91°, and the buried depth is about 7.4 km. The maximum slip of the fault is 0.47 cm located at the depth of 10.6 km. The cumulative seismic moment is 3.89×10¹⁸ N·m, approximately to M_W6.33. Finally, based on the fault slip of the main shock, we calculated the coulomb stress changed on surrounding faults, which shows the coulomb stress on Zepu fault exerted by the main shock increased significantly. The aftershocks for 3 years following the mainshock concentrate the zones where the coulomb stress increased, indicating that the main shock has a certain stress triggering effect on the occurrence of the local aftershocks.

Key words: Pishan Earthquake, InSAR, GPS, MPSO algorithm, Coseismic slip distribution, Coulomb stress