Study on the focal mechanism and deformation characteristics for the 2008 Mw6. 7 Wuqia earthquake, Xinjiang by InSAR

A magnitude M(w)6. 7 earthquake took place in the joint area of the southern Tienshan Mountain, the Pamir Plateau and the Tarim Basin on October 5, 2008. The focal mechanism of this event is investigated by many scientists and organizations, but the epicenter depth is much different. We use PALSAR images from the ALOS satellite to derive the coseismic deformation field. The geometry of rectangular dislocation elements and its slip distributions are inverted based on InSAR-derived LOS and Azimuth coseismic changes by using a half-space homogenous elastic model and Bounded Variables Least Squares (BVLS) algorithm. The results indicate that the moment magnitude of Wuqia earthquake is about M(w)6. 6 and the rupture is dominated by an inverse fault with a maximum slip similar to 3. 4 m at 73. 8040 degrees E, 39. 5335 degrees N and with depth of 5 km. Most displacements are confined to 2 similar to 7 km underground. The rupture plane is about 30 km X 14 km with strike N46 degrees E and dip 48 degrees to NE. The shallow focal depth is possibly resulted from the unreleased stress accumulation from history earthquakes around the seismic fault. At the same time, slip pattern implies that the rupture is composed by two point source models with magnitude M(w)6. 5 and M(w)6. 1, respectively, which has a good correspondence with main shock and aftershock of Wuqia earthquake. Alternatively, the slip pattern may be caused by two ruptures of the main shock.