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 palaeo-seismic 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 palaeo-seismic 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 palaeo-seismic activities and palaeo landslide evolution near the Litang area.