Study on the risk background of strong earthquake in Kangding-Moxi fault, Sichuan

In this paper, the strong earthquake risk of the Kangding-Moxi fault on the Xianshui fault zone in western Sichuan is analyzed and discussed. The fault is located at the arc top turning point of the third arc extrusion structural belt from western Sichuan to eastern Yunnan, where the stress is highly concentrated, the block has a large left-lateral slip, and the range of vertical differential movement between the two sides of the fault is up to 1000-2000 m. It is a seismic area with high fault activity within the continental plate. The Xianshuihe fault zone is a left-lateral strike-slip fault zone with high seismicity and repeatability in China. In the nearly 300 years since 1725, two periods of seismicity have repeatedly occurred on the Xianshuihe fault zone, and the earthquake repetition period is 100~200 years. The Kangding-Moxi fault occurred a large earthquake of magnitude 7¾ in 1786. It has been 237 years since the earthquake occurred, and the fault has been in a relatively quiet period of energy accumulation. Recent earthquakes have become active. After the M6.8 Moxi Town earthquake in Huding, Sichuan Province in September 2022, medium and small earthquakes with M < 5.6 occurred frequently and distributed along the Moxi fault, does it indicate that the fault is active again and enters a new seismicity period? These characteristics indicate that the Kangding-Moxi fault has the background conditions for the occurrence of large earthquakes.