Shear wave splitting and the features of the crustal stress field in the Capital Circle
LAI Yuan-Gen~1,LIU Qi-Yuan~1,CHEN Jiu-Hui~1,LIU Jie~1,LI Shun-Cheng~1,GUO Biao~1,HUANG Zhi-Bin~21 State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China2 China Seismic Network Center, China Earthquake Administration, Beijing 100036, China
In recent years, much attention has been paid to the shear wave splitting caused by the medium cracks. In this study we investigate the S-wave splitting at the stations of the Capital Circle area from the local event data recorded by the permanent and movable seismic network. In this presentation we give the fast polarization directions and the maximal compressive stress direction at the stations in the Capital Circle. The 2_D numerical modeling in terms of the finite element technique demonstrates that the crustal stress field of the Capital Circle can be separated into the NE trending regional stress field and the NW trending local stress field controlled by the Zhangjiakou-Penglai faults. The direction of the maximal principal compressive stress nearby Beijing and Tianjin is toward NE60°～70°, and that nearby Tangshan and its eastern side is toward the EW direction. For the local stress field, the direction of the maximal principal stress is toward 120°～130°, which is roughly parallel with the strike of the Zhangjiakou-Penglai faults. Our numerical modeling demonstrates that the local crustal stress field in the Capital Circle is caused mainly by the Zhangjiakou-Penglai faults.
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