Abstract: To forecast and assess the hazard mechanism of catastrophic landslides, based on the data of earthquake and rainfall-induced catastrophic landslides, the relationships including the equivalent friction coefficient (H/L), the maximum horizontal distance (L), the maximum vertical distance (H) and the landslide volume (V) are studied. The relationships among H/L, L, H and V are power laws, in which there are negative power laws between H/L and V and the positive power laws among L, H and V. The horizontal and vertical movement distances of the seismic and the rainfall catastrophic landslides are different in the same scale. The H/L=0.42 is taken into consideration in the standard of landslide long-runout. It is not significant between seismic induced catastrophic landslides and the landslide long-runout, but there is remarkable relationship between rainfall induced catastrophic landslides and the landslide long-runout. The dominate distance of landslide movement can be analyzed based on the movement distances of the 80% landslides; the dominant distances of the horizontal and vertical movements of seismic and rainfall catastrophic landslides are different in the same scale. The results indicate that the movement distances of catastrophic landslides are not only controlled by the volumes but also related to occurrence mechanism. And they can provide references for forecasting and evaluating the hazard region and strength induced by the earthquake and the rainfall catastrophic landslides.

Key words: seismic landslides, rainfall landslides, equivalent friction coefficient, maximum horizontal distance, maximum vertical distance