Source rupture characteristics of the September 5, 2022 Luding MS 6.8 earthquake at the Xianshuihe fault zone in southwest China

Abstract

On September 5, 2022, at Beijing time 12:52 p.m., an MS 6.8 earthquake struck Luding County, Garze Tibetan Autonomous Prefecture, Sichuan Province. The epicenter of the earthquake was at the intersection of the Sichuan-Yunnan, Bayankala, and South China blocks. The tectonic background is extremely complex, and strong earthquakes occur frequently. Based on a predetermined focal location and focal mechanism solution for the earthquake, we reversed the focal depth and rupture process of the earthquake by fitting the teleseismic P and SH waves recorded by the global seismic network. The results show that the focal depth is 16 ​km, with the main rupture having a length of about 45 ​km near the epicenter, with a maximum displacement of 1.02 ​m. Although the rupture mainly propagates from the north–northwest (NNW) to the south–southeast (SSE) along the fault strike, there is a small-scale rupture slip zone at shallow depths in the north–northeast (NNE) direction along the epicenter of the seismogenic fault. This rupture image corresponds to the cluster distribution of aftershocks in the NNW and SSE directions starting from the epicenter, corresponding to the distribution of recorded landslides. The earthquake occurred on the Moxi fault, located in the southeastern section of the Xianshuihe fault. The major tectonic feature in this area is the southeastward movement of the Chuandian block relative to the Bayanhar block.