Simulation of a long-runout rock avalanche triggered by the Lushan earthquake in the Tangjia Valley, Tianquan, Sichuan, China

Abstract

Only one long-runout rock avalanche was triggered by the 2013 Lushan earthquake in the Tangjia Valley, Tianquan, Sichuan, China. The rock avalanche involved the failure of ~530,000m3 of sandstone from the source area. The displaced material travelled a horizontal distance of ~1600m with an elevation descent of ~480m, equivalent to a fahrböschung of 16.7°. Based on a detailed field investigation, we introduce basic characteristics of the rock avalanche and find that the rock avalanche resulted in one run-up in the Chunwojian Valley, a superelevation in the Gangoutou Valley, and increase in volume due to the entrainment of path materials. A numerical model (DAN3D) was used to simulate the post-failure behavior of the rock avalanche. By means of trial and error, a combination of the frictional model and Voellmy model is found to provide the best performance in simulating this rock avalanche. The simulation results reveal that of the rock avalanche lasted approximately 160s and an average velocity of 10m/s.