Seismogenic fault segmentation of Tangshan earthquake sequence derived from focal mechanism solutions

Based on the method of tectonic stress field homogeneity, this paper determined the segmentation of the seismogenic fault of Tangshan earthquake sequence by using the focal mechanisms of earthquake with M_L≥2.5 occurred in Tangshan area from January of 2002 to November of 2015. According to the previous subarea results related to focal mechanisms in Tangshan area, this paper obtained five reference stress tensors, and the seismogenic fault of Tang-shan earthquake sequence was divided into four segments, i.e., Ninghe, Tang-shan, Luanxian and Lulong, by the significant difference analysis of z-test of cumulative misfit. The inversion for stress fields of the four segments shows the orientation of maximum principal stress axes is nearly in EW, and the stress filed of the Tangshan, Ninghe and Lulong segments showed a greater tensile component. The best stress tensors of Tangshan and Ninghe segments are consistent with the tensile stress field caused by the Tangshan main shock's pulling the northeastern and southwestern ends of Tangshan fault zone. The uplift model of upper mantle material derived from receiver function may also conform to the stress field of Tangshan segment. The strike-slip stress field of Luanxian segment is closely related to the conjugated structure in this area. The best stress tensor of Lulong segment is normal fault with right-lateral strike-slip. From the present characteristics of stress field for the seismogenic fault segmentation of Tangshan earthquake sequence, it is concluded that the seismicity in Tangshan area has inherited the development mode of Tangshan earthquake sequence, and mainly can be controlled by the regional tectonic stress field and the coexistence of deep and shallow faults.