Nature and timing of a prehistoric giant landslide on the eastern margin of the Tibetan Plateau

Studying the characteristics of a prehistoric giant landslide and ascertaining its relationship with palaeo-seismic events could provide useful information on the role of regional tectonic activities in hillslope evolution. Here, a giant palaeoseismic landslide (GPSL), namely, the Luanshibao (LSB) landslide, located on the eastern margin of the Qinghai-Tibet Plateau, was investigated to ascertain its characteristics and occurrence age. The relationship between occurrence age and palaeoseismic episodes was also discussed by using 14C dating on the adjacent active faults, including the regional Yidun-Litang-Dewu (YD-LT-DW) fault zone, which crossed the LSB landslide. The dating of multiple samples acquired from palaeo-seismic trenches revealed that at least 5 palaeo-seismic episodes had occurred in the vicinity of the LSB landslide over the last 5000 years. The occurrence age of the LSB landslide (3635 +/- 387 a BP) coincides with palaeo-seismic episode I, and the LSB landslide is convincingly inferred to have been triggered during episode I, which reached a seismic intensity (Chinese scale) of at least degree VII near the LSB landslide during failure. The timing of a second reactivation phase coincides with palaeo-seismic episode IV, which occurred at 2100-2200 a BP. The study could provide reference for studying the regional palaeoseismic activities and palaeo landslide evolution near the Litang area.