Failure probability assessment of landslides triggered by earthquakes and rainfall: a case study in Yadong County, Tibet, China

Abstract

Yadong County located in the southern Himalayan mountains in Tibet, China, is an import frontier county. It was affected by landslides after the 2011 Sikkim earthquake (Mw = 6.8) and the 2015 Gorkha earthquake (Mw = 7.8). Casualties and property damage were caused by shallow landslides during subsequent rainfall on the earthquake-destabilized slopes. Existing researches have generally examined rainfall- and earthquake-triggered landslides independently, whereas few studies have considered the combined effects of both. Furthermore, there is no previous study reported on landslide hazards in the study area, although the area is strategically applicable for trade as it is close to Bhutan and India. This study developed a new approach that coupled the Newmark method with the hydrological model based on geomorphological, geological, geotechnical, seismological and rainfall data. A rainfall threshold distribution map was generated, indicating that the southeast part of Yadong is prone to rainfall-induced landslides, especially when daily rainfall is higher than 45 mm/day. Permanent displacement predictions were used to identify landslide hazard zones. The regression model used to calculate these permanent displacement values was 71% accurate. Finally, landslide probability distribution maps were generated separately for dry and wet conditions with rainfall of varying intensities. Results can serve as a basis for local governments to manage seismic landslide risks during rainy seasons.

Capturing the footprints of ground motion in the spatial distribution of rainfall-induced landslides

“…Besides, several studies suggest a possible link between these long periods where we observe an elevated landslide susceptibility and large co-seismic landslide deposits (e.g. Chen et al 2020a;Fan et al 2018;Xiong et al 2020;Yunus et al 2020) estimated to sum up to 2.8 km 3 specifically for the Wenchuan case (Li et al 2014). As regards the factors controlling the length of the period characterized by the elevated landslide susceptibility, Fan et al (2018) refer to possible contributions of various processes such as progressive strengthening of the deposits due to grain coarsening (Hu et al 2018) and, in particular, revegetation (Chen et al 2020b;Yunus et al 2020).…”

“…However, the coupled effects of earthquakes and rainfall are rarely examined (e.g. Bontemps et al 2020;Chen et al 2020a;Saemundsson et al 2018;Sassa et al 2007).…”

“…Specifically, for the 2008 Wenchuan earthquake, the post-seismic landslide evolution has been examined in several articles (e.g. Chen et al 2020a;Tang et al 2016;Xiong et al 2020;. For instance, Fan et al (2018) assess postseismic slope failures for a subset of the area affected by landslides since 2008 and until 2015.…”

“…Fan et al (2018) also note that the recovery of the landslide rate to pre-earthquake periods may be longer in areas affected by stronger earthquakes. Chen et al 2020a) examine another subset of the area affected by co-seismic landslides for the Wenchuan earthquake, in the period between 2008 and 2018. And, they report that hillslopes and landslide deposits largely stabilize 10 years after the earthquake.…”

New insight into post-seismic landslide evolution processes in the tropics

“…Nevertheless, characterizing these interactions is critical to advance effective landslide susceptibility assessment because various studies show that the combined effect of earthquakes and rainfall could increase landslide susceptibility (e.g., Sassa et al 2007;Saemundsson et al 2018; Wistuba et al 2018;Bontemps et al 2020;Chen et al 2020a).…”