Abstract:Based on seismic data provided by Hebei regional seismic network, we use the CAP waveform inversion method to obtain the focal mechanism of the July 12, 2020 Tangshan MS5.1 earthquake. In order to get a more accurate focal depth, we employ the depth phase sPL fitting method to measure the focal depth. The results show the parameters of the focal mechanism solution of the mainshock are strike 143°, dip 83°, rake -14° for the nodal planeⅠ, strike 235°, dip 76°, rake -173° for the nodal plane Ⅱ, and centroid depth is 14 km. The result of the focal depth is 14 km by sPL phase method, which is the same as that measured by the methods of CAP. Combined with distribution of earthquake sequence, the seismic intensity map, tectonic setting and deep seismic reflection profiles, we conclude that the nodal plane Ⅱ is the seismogenic fault plane of this earthquake and the Tangshan-Guye fault is the control fault.