Distribution characteristics and cumulative effects of landslides triggered by multiple moderate-magnitude earthquakes: a case study of the comprehensive seismic impact area in Yibin, Sichuan, China

Sichuan Province, as one of the active seismic regions in China, has historically suffered from strong earthquakes. The Xingwen Ms5.7 earthquake in 2018 and the Changning Ms6.0 earthquake in 2019, two moderate-magnitude earthquakes that occurred in Sichuan Province in recent years, happened in quick succession and triggered numerous landslides under similar geological structural conditions. These events provide a rare case study for researching the distribution characteristics and cumulative effects of landslides triggered by multiple earthquakes. This study aims to explore the distribution characteristics and superposition effects of landslides from these two earthquakes and to reveal the complexity and regularity of landslides triggered by multiple moderate magnitude earthquakes by comparing and analyzing the spatial distribution, scale size, and influence factors of landslides from the two earthquakes. The results show that 455 landslides were triggered by the Xingwen earthquake event and 511 landslides were triggered by the Changning earthquake event. The landslides are all mainly small and medium-sized, covering a total area of about 2.33 km², with similar area frequency distribution trends. There is a certain correlation between the number and area of landslides and each factor. In addition, the landslides are mainly distributed in the middle and lower slopes of slower slopes, and the landslide H/L values are positively correlated with the slope gradient. This study reveals the spatial distribution characteristics and morphological parameter features of landslides triggered by the two earthquakes and their aftershocks, which provides a reference basis for landslide hazard assessment and risk management, as well as a case study and inspiration for the study of landslides under the action of multiple earthquakes.