Double difference location of the Ludian M_s6.5 earthquake sequences in Yunnan province in 2014

The earthquake sequences within sixteen days of the Ludian Ms6.5 earthquake in Yunnan province are relocated by double difference algorithm.The relocation results show that the mainshock is located at 27.11°N,103.35°E and the focal depth is about 15 km;the earthquake sequences are distributed dominantly "L"-shaped in the SSE and EW direction,and show nearly vertical focal depth distribution,indicating it is a strike-slip earthquake and has two rupture planes in different directions.Although the Ludian M_s6.5 earthquake occurs near the NE-directed Zhaotong fault and its back thrust faults(Longshu fault and Dayandong fault),these faults are thrust faults and cannot be the seisrnogenic fault.This earthquake occurs in the junction region where multiple faults are distributed in radial pattern;the SSE-directed rupture branch has coincident strike with the Baogu' nao fault,while the nearly EW-directed rupture branch has coincident strike with the south part of the Xiaohe fault.The Ludian M_s6.5earthquake may have connected the Baogu'nao fault and the Xiaohe fault in depth.