Impact of slope stability changes on landslide activity near the epicenter of the 2008 Wenchuan Ms8.0 earthquake, China

Strong earthquakes in mountainous regions can trigger massive landslides, and not just during the period of shaking. This study uses a time series of remote images to better understand the distribution of landslides near the epicenter of the 2008 Wenchuan Ms8.0 earthquake. We use multi-year high-resolution satellite images to interpret landslides and establish landslide inventories spanning from 2008 to 2019. Based on differencing pre-earthquake and post-earthquake digital elevation models (DEMs), we calculate the factor of safety (F-s, i.e., resisting forces versus driving forces) of slopes using a simplified Newmark model. Results show that landslide occurrence highly relies on slope stability, demonstrated by both co-seismic and post-seismic landslide mapping. According to the F-s analysis, which is closely related to the gradual slope change after the earthquake, most slopes within the study area stabilized after the 2008 Wenchuan earthquake, consistent with the decreasing trend of the landslide activity level. However, due to lithologic variation, the changes of post-earthquake slope stability may differ with landscape features in various regions and result in different geologic hazards. Thus, we highlight the necessity of continuous post-seismic monitoring and analysis of slope stability in different affected regions. The results of this work provide useful information for post-seismic infrastructure reconstruction and future earthquake disaster prevention in mountainous areas.