Relocation of Ji'nan 4.1 Earthquake Sequence and Seismogenic Structure Analysis

Based on the phase observation reports of Shandong regional digital seismic network and mobile observation instruments, we relocated the Ji'nan M4.1 earthquake sequences on 18 Feb. 2020 by double-difference location algorithm, and analyzed the sismogenic structure of the sequences by combining the focal mechanism. The results show that the advantage distribution direction is NW. The focal depth concentrated in the range of 3~5 km with an asymmetric bilateral fracture and occurred from shallow to deep. It's focal mechanism reveals that the azimuth of axes P is nearly EW direction and the azimuth of axes T is nearly SN direction which is consistent with the regional stress field. The focal mechanism solution and the relocated result show that the earthquake sequence may be induced by Changqing faults and its secondary faults under the effects of the regional stress field.