The mechanisms of complex morphological features of a prehistorical landslide on the eastern margin of the Qinghai-Tibetan Plateau

Studying the morphological features and triggers of prehistorical giant landslides provides important information about landslide kinematics and dynamics. This study investigates a typical prehistorical giant landslide: the Luanshibao (LSB) landslide on the eastern margin of the Qinghai-Tibetan Plateau. The LSB landslide is a typical long-runout (H/L = 0.207) giant granite landslide detached from a narrow ridge as a wedge failure cut by conjugate fissures that are widespread in the mountain. Two-stage failure produced the current deposit landforms: the first failure occurred at 3675±25~3580±25 a BP; the second failure occurred at 2180±49~2005±25 a BP. These two failures occurred during ancient seismic episodes, and earthquakes were potentially the triggers. The second failure reworked local morphological units of deposits forming the sliding zone (multistage platforms and local scarps), local landslide zone (3 local landslides), and deposit zone (transverse ridges, cross ridges, oblique ridges, and hummocks) due to different mechanical states.