Characteristics and block kinematics of a fault-related landslide in the Qinba Mountains, western China

Abstract The Qiyangou landslide occurred on July 182,010 in the Qinba Mountains of China and resulted in 29 deaths. The landslide or slope failure took place in carbonaceous slate of the upper Ordovician and lower Silurian Banjiuguan Group. A fault coincided with the location of the eastern scarp of the Qiyangou landslide. To study the geological and tectonic characteristics of the landslide, detailed field investigation, terrestrial laser scanner (TLS) survey and the quartz C-axis fabric analysis were conducted. Three-dimensional distinct element modeling was used to determine the potential slope failure mechanisms. The results demonstrated that the mechanism and stability of the slope changed as the internal discontinuity sets changed. The failure initiated on the eastern side along the fault plane and propagated along other pre-existing discontinuities to discontinuity set 1 (DS1). The shear strength of the overall block stability was contributed by the DS1. Based on the results of this study, we postulate that the wedge-planar failure was aided by the pre-existing fault.