Abstract:Located in the southeastern margin of the Tibetan Plateau, Yunnan Province has many active faults. It is a typical historical strong earthquake-prone area. The 1588 Tonghai-Qujiang M7.0 earthquake occurred at the junction of the nearly north-south left-lateral strike-slip Xiaojiang fault zone and the north-west right-lateral strike-slip Qujiang fault zone. The predecessors made the Qujiang fault as the seismogenic fault because of its obvious track, strong activity and the potential of occurrence of large earthquakes with magnitude 7 or above. On the basis of reorganizing the historical data of earthquakes, combining with remote sensing interpretation and surface survey, it is found that the West Branch of the southern part of the Xiaojiang fault zone is not truncated by the Qujiang fault, but is faulted and extends south through the Qujiang fault. Based on the calculation of the recurrence ability of earthquakes with magnitude 7 or above on the Qujiang fault zone, it is considered that the seismogenic structure of the 1588 Tonghai-Qujiang 7.0 earthquake recorded in history should be the southern extension of the Western Branch of the Xiaojiang fault zone. In addition, according to the intensity-magnitude relationship and the surface rupture length-magnitude relationship, the magnitude of the 1588 Tonghai-Qujiang earthquake is calculated about 6.5, which may be overestimated before. Based on the new investigation results, the active tectonic pattern and future seismic risk at the southern end of Xiaojiang fault zone are further reanalyzed. It is considered that there is a relationship between the southern segment of Xiaojiang fault zone and the Qujiang-Shiping fault zone, which is regarded as a typical structural composite relationship. The intersections of the two groups of faults are often the development parts of tectonic pull-apart basins, forming Gaoda valley, Qujiang basin and Jianshui basin. After reorganizing the historical earthquakes with intensity greater than or equal to Ⅸ, it is found that the north of Jianshui on the Eastern Branch of the southern section of Xiaojiang fault zone is a significant historical seismic gap in this area, so more attention should be paid to earthquake prevention and disaster reduction in the future.