Landslides induced by a combined effect of earthquake and rainfall

Abstract

Many landslides are triggered by rainfall and many landslides are triggered by earthquakes. The probability that rainstorms (typhoons or hurricanes) and earthquakes attack same area is not high or rare. Combined effects of rainstorms and earthquakes have not been examined. The 2004 Mid-Niigata Prefecture earthquake (M6.8) caused twelve landslides more than one million cubic meters, and many landslide dams were formed by large-scale displaced landslide masses. While, the 1995 Hyogo-ken Nambu earthquake (M7.2) did neither cause any large-scale landslide, nor landslide dam although it has a greater magnitude and a similar depth of earthquake. One major difference is: a typhoon attacked Niigata Prefecture in three days before the earthquake, and the 1995 Hyogo-ken Nambu area was very dry before the earthquake. Combined effects of two triggering factors were examined for two cases which the authors investigated: the 2006 Southern Leyte landslide possibly triggered by a nearby small earthquake (M2.6), and the Higashi-Takezawa landslide triggered by the 2004 Mid-Niigata Prefecture landslide. © 2007 Springer-Verlag Berlin Heidelberg.