Recovery of co-seismic deformation from strong motion records during the Wenchuan earthquake

Records from 64 strong motion stations nearly along the Yingxiu--Beichuan fault in Wenchuan earthquake are used as database. Near fault permanent displacement were derived from acceleration records based on baseline correction, and were compared with GPS observation to investigate the ground motion displacement characteristics induced by Wenchuan M_S8.0 earthquake. The following conclusions can be made from our study: ① The ground motion are significant as close to the Yingxiu--Beichuan fault both on the hanging wall and footwall. The permanent displacement from the 51SFB, 51MZQ and 51JYH record on the footwall is westward, with a largest displacement of 1.49 m from the 51SFB record, while the 51WCW record on the hanging wall is eastward with a displacement of 1.26 m. ② Distribution of permanent displacement shows that the movements of both hanging wall and footwall display a dominant direction toward the Yingxiu--Beichuan fault in the Longmen Shan zone, with east-west displacement being larger than north-south one. The fault mechanism is characterized mainly by a thrust motion, and the thrust motion component is much larger than the strike slip, being consistent with the results of seismic source inversion and field investigation. ③ The largest permanent displacements are limited in the narrow rupture zone along the Longmen Shan fault, and reduce rapidly away from the causative fault. It is noted that the permanent displacement in Sichuan basin on the footwall attenuates more rapidly with distance than that on the hanging wall.