The debris avalanche in Donghekou area triggered by the 2008 Wenchuan (M8.0) earthquake: Features and possible transportation mechanisms

Abstract

In 2008, the Wenchuan earthquake triggered many large landslides with rapid movement and long runouts, resulting in a great number of casualties. Although there have been many studies of the geographical features and initiation mechanisms of some catastrophic landslides, the movement mechanisms for many remain unclear. In this paper, we present a case study of a large landslide (debris avalanche) triggered by the 2008 Wenchuan earthquake in the Donghekou area, Sichuan Province, China. We made detailed field surveys of the geographical features of the landslide and carried out subsurface investigations of the landslide deposits using microtremor array measurement and electrical resistivity tomography (ERT). Based on the observed surficial features, shear-wave velocity (Vs) profiles and 2D electrical resistivity profiles of the landslide deposits, we estimated the possible thickness of landslide deposits at different locations, and also analyzed the possible landsliding mechanisms. We inferred that this landslide resulted from retrogressive failures on the source area, and the displaced landslide materials underwent transitional spreading with further entrainment of debris along the travel path. Multiple mud waves might have been formed in the substrate soil layers along the travel path due to the entraining of landsliding materials, and the landsliding materials might have presented channelized movements, indicating that different parts may have moved at different speeds. This kind of transportation mechanism may provide information for elevating the numerical simulation of landsliding, and also for reuse of deposit area of large landslides.