The Focal Mechanism Solution and Seismogenic Structure of the Subei M_S 5.5 Earthquake in Gansu on October 24th, 2023

This article collected broadband seismic waveform and phase data recorded by the Qinghai and Gansu regional seismic networks. The focal mechanism solution and centroid depth of the Subei M_S5.5 earthquake in Gansu on October 24th, 2023 were obtained by performing centroid moment tensor inversion with ISOLA software. The precise hypocenter results and spatio-temporal distribution characteristics of the earthquake sequence were obtained through the double-difference relocation method, and an analysis of the seismogenic structures was conducted based on the structural background of the area. The focal mechanism solution parameters of the Subei M_S5.5 earthquake are as follows: the strike, dip and slip angles of nodal plane I are 170°, 73°and 108°, respectively. The strike, dip and slip angles of nodal plane II are 300°, 24° and 42°, respectively. The main shock centroid depth is 4 km. After relocation, the epicenter of the earthquake sequence was concentrated in a region about 22 km long and 10 km wide, and the dominant direction of the earthquake cluster was NNW-SSE. Based on the analysis of focal mechanism solution, relocation results and regional tectonic background, we infer that the focal mechanism solution plane I is the seismogenic fault plane, and the earthquake is a predominantly thrust faulting with strike-slip event occurring on the hidden fault, and the seismogenic fault has the same property as the surrounding major faults.