Abstract: We obtained the co-seismic deformation fields of the 2008 Yutian M_W7.2 earthquake using InSAR based on ascending and descending orbits of ENVISAT ASAR data. SDM is used to invert the fault slip distribution. Using PSCMP to forward and obtain the simulated NS direction deformation, then combining with the co-seismic deformation fields of ascending and descending orbits to calculate the 3D co-seismic deformation field. The analysis of the co-seismic deformation fields shows that the 2008 Yutian M_W7.2 earthquake is mainly rupturing along the NNE-trending normal fault with a slight strike-slip component. The inversion of the co-seismic slip distribution shows that the fault is divided into four segments along strike, and slip distribution mainly concentrates in 0 to 14 km depth and fault plane of F2 and F3, the largest slip is about 5.31m located in depth of 2.76 km along the fault plane of F2, the ratio of left-lateral strike-slip deformation to vertical deformation along the rapture tends to increase, the inverted seismic moment is about M₀=5.58×10¹⁹ N·m, which is equal to a moment magnitude of M_W7.10. The result of three-dimensional co-seismic deformation field calculation shows that the hanging wall of fault is subsidence deformation, the footwall of fault is uplift deformation, and the subsidence is obviously larger than the uplift, which proves that the earthquake is mainly normal fault. Except that the mid-upper part of the hanging wall near the fault zone moved to ES direction, the hanging wall moved to WS direction, however, the footwall moved EN direction on the whole, which demonstrates that the rupture has left-lateral strike-slip. Forward and inversion of the slip distribution and calculation of three-dimensional deformation field show that the 2008 Yutian M_W7.2 earthquake is mainly normal fault with a significant left-lateral strike-slip.

Key words: InSAR, Slip inversion, 3D deformation field, The 2008 Yutian M_W7.2 earthquake