Distinctive controls on the distribution of river-damming and non-damming landslides induced by the 2008 Wenchuan earthquake

The 2008 Wenchuan earthquake (China, M _w 7.9) highlighted the importance of assessing and mitigating the hazards from co-seismic landslides and landslide dams. The seismic shaking triggered hundreds of thousands of landslides, about 800 of which dammed the course of rivers. To understand whether distinctive factors concurred with the river-damming events, we analyzed the spatial patterns of the river-damming landslides and the non-damming landslides separately, with reference to a number of possible controlling factors. Then, we quantified the significance of these factors using the weight of evidence method, and we used the results to perform a susceptibility assessment in a portion of the earthquake-affected region to verify the effectiveness of the method. We find that the distance to the fault surface rupture, peak ground acceleration (PGA) and lithology play a controlling role for co-seismic landslides of any type. The occurrence of river-damming landslides, rather than by a specific lithology or topography, is more related to hydrological factors, while topographic controls (slope, internal relief and terrain roughness) are more significant for the non-damming landslides.