The post-seismic horizontal and vertical deformations following the 2008 Ms8.0 Wenchuan earthquake are inferred from GPS and precise leveling data. The post-seismic relaxation process is measured using GPS data from campaign stations located around the Longmenshan fault, and the derived decay time constant is 12 days. The evolution of the post-seismic vertical deformation is obtained from precise leveling data measured near the surface rupture. The results demonstrate that the hanging wall is uplifting and the foot wall is subsiding. The amplitude of the post-seismic deformation is lower than that of the co-seismic deformation. The region with the largest post-seismic displacement is located on the leveling route between Maoxian and Beichuan on the hanging wall.
The devastating MS8.0 Wenchuan earthquake ruptured two large parallel thrust faults along the middle segment of the Longmenshan thrust belt.Preseismic and postseismic leveling data indicated the hanging wall of the YingxiuBeichuan-Nanba thrust fault mainly presented coseismic uplift with respect to the reference point at Pingwu county town, and the observed maximum uplift of 4.7 m is located at Beichuan county(Qushan town)which is about 100 m west of the fault scarp.The foot wall of the Yingxiu-Beichuan-Nanba thrust fault mainly showed subsidence with maximum subsidence of 0.6 m near the rupture.By employing a listric dislocation model,we found that the fault geometry model of exponential dip angleδ=88°×[1-exp(-9/h)]with depth of 18 km and uniform thrust-slip of 5.6 m could fit the observed coseismic vertical deformation very well,which verifies the listric thrust model of the Longmenshan orogenic zone.
Qingliang WangDuxin CuiXi ZhangWenping WangJinwen LiuKang TianZhaoshan Song
