Insights into some large-scale landslides in southeastern margin of Qinghai-Tibet Plateau

The Sichuan–Tibet railway (STR), beginning from Chengdu in Sichuan Province and ending in Lhasa in Tibet Autonomous Region, runs across the southeastern margin of the Qinghai–Tibet Plateau (QTP). Due to intense tectonic activity, deeply incised valleys, high geostress and frequent earthquakes, the STR area is of a typical large landslide-prone area. To gain insights into large landslides along the STR, an area covering 3.34 × 105 km2 that extends 80–150 km on both sides of the railway was used to examine the spatial distribution and corresponding characteristics of landslides. The results showed that the study area contains at least 629 large landslides that are mainly concentrated on 7 zones (zones I–VII). Zones I–VII are in the southern section of the Longmenshan fault zone (with no large river) and sections with Dadu River, Jinsha River, Lancang River, Nujiang River and Yarlung Zangbo River. There are more landslides in the Jinsha River section (totaling 186 landslides) than the other sections. According to the updated Varnes classification, 408 large landslides (64.9%) were recognized and divided into 4 major types, i.e. flows (275 cases), slides (58 cases), topples (44 cases) and slope deformations (31 cases). Flows, which consist of rock avalanches and ice–rock avalanches, are the most common landslide type. Large landslide triggers (178 events, 28.3%) are also recognized, and earthquakes may be the most common trigger. Due to the limited data, these landslide type classifications and landslide triggers are perhaps immature, and further systematic analysis is needed.