Catastrophic landslides triggered by the 1950 Medog—Zayu Ms8.6 earthquake in Xizang Autonomous Region, China

On 15 August 1950, an Ms8.6 earthquake struck the Medog—Zayu region in the Eastern Himalayan syntaxis, with a maximum intensity of XII and an area with intensity≥VIII of about 2.19×105 km2. This mainshock-dominated event released seismic energy in a highly concentrated manner and triggered extensive landslides and related geological hazards. To systematically reveal the spatial distribution and the river-blocking patterns of coseismic landslides, we integrate multi-temporal historical imagery since 1961, archival records and field investigations to analyse the intensity distribution. For the high-intensity zone (X–XII) from Milin Wolong to downstream of Duden in the Namcha Barwa region, a coseismic landslide inventory is constructed for the first time, resulting in a dataset of 920 landslides. Quantitative analysis reveals that landslides predominantly occurred at 2 000–4 000 m elevation, on 20°–50° slopes, and within 4 km of active faults. The landslide distribution is strongly controlled by the main central thrust fault, the Motuo fault, and the Apalong fault. Based on statistical analysis and morphological characteristics, we delineate four types of earthquake-induced landslide-damming patterns: seated landslides, high-altitude remote hazards, whole gully-scale landslides and multi-landslide clusters, typified by the Gengbangla, Zelongnong Gully, the Jamaqiming Gully, and Zhaqu—Xirang landslide groups, respectively. The maximum duration of river blockage reached 15–16 hours. The unique geomorphic and tectonic environment of the Eastern Himalayan Syntaxis provides favorable conditions for the occurrence and evolution of high-altitude remote geological hazards. As the region is currently in a seismically active phase, it is critical to enhance research on the failure mechanisms and early warning of under extreme earthquake conditions, thereby improving disaster preparedness, resilience, and emergency response capabilities in the region.