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, located within the Xianshuihe fault zone in western Sichuan, is analyzed and discussed. The fault at the apex of the third arc extrusion structural belt extends from western Sichuan to eastern Yunnan. This area is characterized by high stress concentration, substantial left-lateral slip, and a vertical differential movement between the two sides of the fault ranging from 1000 to 2000 meters. It is one of the most seismically active regions within the continental plate. The Xianshuihe fault zone is a left-lateral strike-slip fault zone with high seismicity and earthquake recurrence in China. Over the nearly 300 years since 1725, two periods of seismicity have repeatedly occurred on the Xianshuihe fault zone, with recurrence intervals of 100 to 200 years. The Kangding-Moxi fault was the site of a major earthquake, with a magnitude of 7¾, in 1786. It has been 237 years since that event, and the fault has been in a relatively quiet phase of energy accumulation. However, recent earthquakes have become active. Following the MS6.8 Moxi earthquake in Luding, Sichuan Province in September 2022, medium and small earthquakes with M<5.6 occurred frequently and along the Moxi fault. This raises the question of whether the fault is reactivating and entering a new period of seismic activity. These characteristics indicate that the Kangding-Moxi fault has the background conditions for the occurrence of large earthquakes.