Nonuniform velocity model used in the relocation of Wenchuan Ms 8.0 earthquake and aftershocks

To further explore the depth structure of the Longmenshan fault zone,according to the original seismic data from the Sichuan Seismological Bureau,the authors relocated the Wenchuan Ms 8.0 earthquake and M≥2.0 aftershocks using the position methods of Hypo 2000.By the end of April 15,2011,26278 earthquakes were recorded.After relocation,the results were summarized as follows:(1) The main shock occurred on the Beichuan-Yingxiu fault in the middle sector of the central fault of Longmenshan nappe structural belt and the aftershocks extended along the direction of the fault zone,presenting a distribution of north and south segments.The residual error after relocation is ±0.35 s,the level of error is ±1.32 km,and the depth error is ±5 km.(2) There is a north-west aftershocks belt along Yingxiu-Lixian-Heishui near the main shock which is coincident with the Longmenshan tear fault.(3) The vicinity of Qingchuan(the north end of the Longmenshan fault zone) becomes the aftershocks dense areas,which are not coincident with the fact that few earthquakes occurred in this region in history.