Abstract: Using seismic phase data and waveform data of M_S≥4.0 earthquakes among Lushan earthquake sequence from April 20 to May 20, 2013, we obtained precise locations of 3398 earthquakes by using double-difference earthquake location algorithm, and the moment tensor solutions of 17 earthquakes by utilizing the time-domain full waveform inversion method. Based on a comprehensive analysis of the double-difference relocation and focal mechanism solutions of middle to strong earthquakes in the Lushan earthquake sequence, we find that the seismogenic structure of the Lushan earthquake consists of a main shock fault and a secondary thrust fault. The main shock fault is a high-angle thrust fault striking NE, trending NW, and dipping approximately 45 degrees. The secondary thrust fault is the same direction with the main shock in strike, and opposite in trend. And the two faults are not exposed to the surface. Both the main shock and aftershock focal mechanism solutions are thrust-type, with almost no slip component. The direction of principal stress in the source area is NW, which is perpendicular to the seismogenic fault.

Key words: Fault structure, Stress field, The 2013 Lushan M_S7.0 earthquake sequence