摘要
Through the field investigation,focal depth checking and focal mechanism solutions inversion etc. ,we conducted a comprehensive research on the Weihai earthquake sequence on Jul. ,2011,and then inversed the focal mechanism solutions of earthquake sequence by P-w ave first motion method. The results show that source rupture mode of Weihai earthquake sequence is strike-slip,the nodal plane I ( NE striking) maybe the fracture surface, and the occurrence of earthquake swarm is controlled by the fault in NE direction. Through identifying the Pn phase and sPn phase of the ML 3.5 earthquake,we calculated its focal depth and deduced it occurred in the upper crust. Because the focal depth is shallow ,the seismic intensity investigation shows that the maximum seismic intensity in epicenter area reached Ⅴ-degree.