Distribution pattern, geometric characteristics and tectonic significance of landslides triggered by the strike-slip faulting 2022 Ms 6.8 Luding earthquake

Abstract

On September 5th, 2022, an Ms 6.8 earthquake struck the Luding area of Gaze Tibetan Autonomous Prefecture, Sichuan Province, China. This earthquake with a focal depth of 16 km at 29.49°N, 102.22°E (hereinafter called the Luding earthquake) was generated by a strike-slip faulting and triggered at least 5000 landslides over an area of 5000 km2. Over 80 % of landslides are distributed in areas with a seismic intensity of IX, which mainly consist of massive shallow landslides with a few topples, rockfalls, and debris flows. Statistically, coseismic landslides are prone to occur in areas with low elevations, steep hillslope gradient, and high ground motion, and most of them are distributed in four landslide abundance areas, including the Moxi area (Sub-1), the Wandong area (Sub-2), the Wanggangping area (Sub-3) and Xingfu area (Sub-4). Among them, the landslide scale and abundance index peaks in the Sub-2 and Sub-4 areas featured by the low-elevation valley landform with large relief and steep slopes. The geometric parameters of landslides show that the majority of landslides have the height difference between 15 and 150 m and a movement distance between 50 and 250 m. As the landslide area increases, the length and height of the landslide follow a growth trend which can be described by the logarithmic relationship. Compared to other strike-slip seismic events, the Luding event has the more obvious ability to trigger coseismic landslides. The spatial distribution of coseismic landslides is controlled by the seismogenic fault, and over 85 % of landslides are roughly distributed within a range of 5 km on both sides of the seismogenic fault. Overall, the west side of the seismogenic fault has higher landslide abundance and pronounced near-surface rupture, and it thus can be inferred that the seismogenic fault dips slightly westward based on the source mechanism solution and actual landslide distribution.