Geomorphic and tectonic controls of landslides induced by the 2022 Luding earthquake

On 05 September 2022, an Ms 6.8 (Mw 6.6) earthquake occurred in Luding County, Sichuan Province, China, with the epicenter at 29.59°N, 102.08°E and a focal depth of approximately 16.0 km. Combining field investigations, high-resolution satellite images and multiple datatpes characterizing the seismogenic structure, topography and geology, this study attempts to discuss the influence of geomorphic and tectonic indexes on landslide distribution. The results show that the 2022 Luding earthquake with seismogenic fault at the Moxi fault, was a sinistral strike-slip event that triggered at least 4528 landslides over an area of ~2000 km². These landslides span a total area of 28.1 km², and the western section of the seismogenic fault, which serves as the active wall area, is characterized by a higher landslide concentration, especially in the Wandong Basin. The seismogenic fault and lithology influence the regional distribution of landslides, and more landslides occurred closer to the seismogenic fault and in the controlling lithologies of granite and dolomite. Local topography influences the landslide occurrence position on the slope; the eastern section is prone to form landslides in the lower gorge section, and the western section is prone to form landslides in the upper-top section of the gorge. For coseismic landslides in the eastern Baryan Har block, the eastern boundary (Longmenshan fault), where the earthquakes are characterized by thrusts with slight dextral strike-slip movement, could be the primary landslide-prone area; the southern boundary, the Moxi fault and the southern segment of the Xianshuihe fault, with more intensive strike-slip movement, may be the secondary landside-prone area; and the northern boundary is the tertiary landside-prone area. Additionally, the current landslide inventory may be underestimated although this underestimation has limited influence on the results.