A Model of In-depth Displacement under Ms8.1 at Kunlun Earthquake with D-InSAR Co-seismic Deformation Field

Numerical modeling can be used to obtain geophysical information for earthquake mechanism analysis. During the past decade, differential synthetic aperture radar interferometry (D-InSAR) technology has been applied successfully to research co-seismic field and hypocentral mechanism, which could offer more abundant boundary conditions with higher quality as compared with the conventional methodology of geodetic measurement. This paper reports a model of in-depth co-seismic displacement with this approach. By means of Poly3D, a geophysical boundary element method (BEM) developed by Stanford University, and based on the boundary conditions of D-InSAR hypocentral parameter, this paper simulates a 3D distribution of the co-seismic deformation and spatial trend of displacement vector over the shock surface area of 80,000 km² and its underground areas of 20 km in depth. The 3D displacement field shows that the maximum strike displacement Ux occurs at 15 km below the surface of the Hoh sai Hu lake east-Yuxi peak segment, with a maximum dislocation of 6.424 m, the maximum dip displacement Uy is located 10 km below the surface of the Yuxi peak-Kunlun Mountain Pass segment, with a maximum dislocation of 2.067 m, and the maximum dip displacement Uz is located 10 km below the surface of the Yuxi peak-Kunlun Mountain Pass segment with a maximum dislocation of 3.701 m. The simulation displacement vectors indicate that bounded by the almost vertical main rupture plane, the south wall thrusts northward with some subsidence, the north wall moves upwards, the south wall moves from west to east while the north wall does from east to west. As the horizontal offset is dominated by left-lateral vertical displacement, the earthquake is classified as a strike-slip dominant type. Thus it is concluded that the Ms8.1 Kunlun earthquake originated from the Kunlun fault with a set of steep dip, left-lateral and strike-slip reverse faults.