Geological and geomorphological characteristics of catastrophic landslides induced by recent earthquakes

摘要

Many of the large landslides induced by recent earthquakes were preceded by previous movement, providing a geomorphological clue for their prediction, while some type of landslides occurred without preceding deformation but in specific geologic conditions. Landslides, which were preceded by previous movement, occurred on slopes with geomorphic features of gravitational deformation, such as ridge-top depressions. Previous landslides, once collided to the opposite slope and later undercut, are very susceptible to earthquake. Catastrophic landslides without preceding movement occurred on slopes underlain by valley-fill sediments, carbonate rocks, or pyroclastics particularly pumice. Valley-fill sediment slides are probably due to liquefaction or pore water pressure buildup. Pumice is weathered to become so weak that it is easily broken by earthquake shaking. Carbonate rocks are dissolved by the groundwater and decrease the area of contact surfaces along discontinuities and consequently its strength.