CLASSIFICATION AND SUDDEN INITIATION MECHANISM OF LARGE LANDSLIDES TRIGGERED BY 2008 WENCHUAN EARTHQUAKE

2008 Wenchuan earthquake triggered more than 300 large landslides followed by huge loss of life and property, which emphasizes that study on their forming mechanism has a great significance in theory and practical application for disaster prevention and mitigation. By field investigation and analysis on published material about the landslides, a new term landslide-quake is defined in this paper. It is different from Whenchuan mainshock by its effect on the forming of the landslides. This paper looks into the evidences, formations and characteristics of landslide-quake. It gives different combinations of landslide-quake and earthquake. It finds that these large landslides triggered by 2008 Wenchuan earthquake can be classified into the following three types.(1)Normal earthquake landslide, for which no landslide-quake occurs and the main contributing forces are earthquake force and the gravity of sliding mass.(2)During earthquake landslide, for which a landslide-quake generates during the earthquake and the main contributing forces are landslide-quake force, earthquake force and the gravity of sliding mass.(3)After-earthquake landslide, for which a landslide-quake generates after the earthquake and the main contributing forces are landslide-quake force and the gravity of sliding mass. The opinion is suggested that the process of large landslide generation is similar to the sudden cut of a seismic fault and the estimation of the magnitude of a landslide-quake and the provided shearing force. Based on the above, the processes of the sudden initiations of these three kinds of landslides are analyzed. The concept of landslide-quake is a new explanation for the mechanism of sudden initiation of a large rapid landslide, and it, along with the other results of this study, provides a reference for large rapid landslide research.