Analysis on the Focal Mechanism and Seismogenic Structures of the Yao’an earthquake with M_S6. 0,20091

Using the joint inversion method with the amplitude ratio of P-wave,SV-wave and SHwaves,this paper calculates the focal mechanisms of the aftershock sequence of the Yaoan earthquake with MS6. 0. According to the spatial distribution of earthquake sequence,the author analyzes the characteristics of the stress field and seismogenic fault. The result shows that:( 1) the seismogenic fault of the Yaoan earthquake is a vertical right-lateral strike-slip fault,striking NWW-SEE. The result is reliable and consistent with the nodal planes of the Harvard CMT solution and also in accord with the predominant direction of aftershocks.( 2) The predominant direction of principal compressive stress,NWW-SEE is consistent with the regional tectonic stress,and some aftershocks are different from the main shock. The stress field of the main shock is controlled by the regional tectonic stress field,indicating the diversity and complexity in the seismic area.( 3) By comprehensively analyzing the distribution of the earthquake sequence,focal mechanism and fault structure in the seismic area,it is found that the Maweijing fault is the seismogenic fault of the Yaoan earthquake.