Characteristics of P-wave velocity distribution in Yangbi seismic source area based on dense array

Based on the seismic phase arrival time of the Dali Earthquake sub-instability seisimc network in Yunnan province, the P-wave velocity structure of the Yangbi MS6.4 earthquake in 2021 in Yunnan Province was inverted by double-difference tomography, and then the seismogenic structure of the earthquake was analyzed. Both ray distribution and checkerboard test show that the Yangbi seismic source area is well covered by the sub-instability network. In the depth range from 2 km to 16km, the resolution of P-wave velocity model becomes better and better with the increase of depth, and the resolution in the source area can reach 0.1°×0.1° . The velocity structure of the Yangbi MS6.4 earthquake occurred in the high velocity body near the boundary between high and low velocity, and the seismic sequence mainly distributed along the NW-SE direction, which was basically parallel to the Weixi-Qiaohou fault. There are low velocity anomalies in the north and south of the Yangbi earthquake sequence, and the high velocity anomalies may block the NW-trending rupture of the Yangbi earthquake, thus causing the SE - trending rupture of the seismic sequence.