Interaction among controlling factors for landslides triggered by the 2008 Wenchuan, China Mw 7.9 earthquake

The 12 May 2008 Mw 7.9 Wenchuan, China earthquake triggered about 200,000 landslides, which were controlled by a number of factors. This study examines five factors: slope angle, slope aspect, lithology, peak ground acceleration (PGA), and fault side (relative position on the seismogenic fault, i.e., hanging wall or footwall), to determine how these factors control the co-seismic landslide occurrence and whether one or more factors, acting alone or in concert, are involved in promoting or suppressing landslides. We performed a multi-factor statistical analysis using data from the 2008 Wenchuan earthquake. The results show that in the areas characterized by steep topography or where strong ground shaking occurred during the earthquake, there is a closer relationship between slope aspect and landslide number density (LND) than other areas. The relationship between lithology and LND values depends on PGA. In turn, the relationship between LND values and PGA is also influenced by lithology. In addition, the controlling effect of lithology on co-seismic landslides on the hanging wall of the seismogenic fault is greater than that on the footwall. Examining interactions among these factors can improve understanding of the mechanisms of co-seismic landslide occurrence.