Abstract:Rupture behaviors of (paleo) earthquakes are the basic data for seismic risk assessment and seismic design of major engineering constructions. Xianshuihe fault is the most active left-lateral strike-slip fault of the southeastern margin of the Tibetan Plateau. An earthquake of magnitude 7 or higher occurred every 30 years on average. Kangding Downtown area where the proposed Sichuan-Tibet Railway passing through is a relatively weak segment of Xianshuihe fault in paleo-seismic research. In order to obtain more detailed rupture characteristics and recurrence behaviors, we selected a depression pond at the Xinyulin site on the south side of Kangding new town to excavate the trench group. Two trenches arranged perpendicular to the fault pond were designed and studied, each trench with a total length of 18 meters, 3 meters deep, and 3 meters wide. Five meters wide rupture zone, seven sets (three categories) of sedimentary strata with clear boundaries and a series of paleoearthquake remains such as structural wedges were revealed in the trenches. According to the division of stratus and the relationship between faults and stratus, a total of 6 rupture events were summarized in the trenches, Combining the twenty ¹⁴C AMS dating results and historical seismic records, the events were limited in order: before 8714BC, 8304-6316BC, 6135-734BC, 118BC-27AD, 810-1230AD, and Kangding South M7¾ earthquake event in 1786. The modeled date shows that Near Xinyulin Village, the early recurrence interval of rupture events is relatively long (about 3000 years), and the activity has intensified since around AD, the recurrence interval has been shortened to about 700～1000 years, which is basically the same as the large earthquake recurrence habits in the North segment of Xianshuihe fault Belt. Comparison and synthesis with the previous research results, most of the events from Xinyulin to Ertaizi south of Kangding, Xianshuihe fault ruptured at the same time, but there may be some events that only ruptured near Ertaizi. Since 1893, Xianshuihe fault has entered a significant active period again. Destructive earthquakes have occurred in the northern segment of the Xianshuihe fault zone, while the southern segment of Kangding has been calming since the Moxi earthquake in 1786, and there is a possibility of strong earthquake with surface rupture in the future. Along the construction and operation of Sichuan-Tibet Railway, the monitoring and early warning of major earthquakes should be strengthened.