Teleseismic P Wave Tomography on the Crustal and Upper Mantle Structure in Cangzhou Area

We used 2308 P wave arrival times from 271 teleseismic events recorded by the 20 portable seismic stations during December 2006 to July 2010 in Cangzhou region, Hebei Province. By using seismic tomography method, we got the 3-D crustal and upper mantle P wave velocity structure in Cangzhou and its adjacent area (38.0°N~39.0°N, 116.5°E~117.5°E). Teleseismic tomography results reveal that the significant lateral variations for the velocity distributions in crust on both sides of Cangdong fault zone. The shallow velocity distribution is consistent with the distribution of the surface geological structure. Cangxian uplift in the northwest of Cangdong fault zone is with the higher velocity values in the crust, indicating that it has the uplift basement. Huanghua depression in the southeast of the fault zone is with lower velocity, indicating the substrate buried deeper. These results and previous gravity, electromagnetic and artificial seismic exploration results all show that the Cangdong fault zone is in obvious changes in the geological structure and geophysical properties, which could be displayed in whole crust.