Landslides triggered by the 1995 Hyogoken-Nambu earthquake were reviewed based on air photo interpretation for their distribution. Landslides were almost linearly distributed along the line of aftershocks. Most landslides showed limited motion probably affected by less saturated soil condition due to the very dry season. The Osaka group layer, however, retained the ground water and rapid landslides took place there. The Nikawa landslide and the Takarazuka landslide were investigated as case histories. The undrained cyclic loading ring shear test suggested that this landslide showed a rapid motion due to the high pore pressure generation caused by grain crushing along the sliding surface. It can be called “sliding-surface liquefaction”.
The trench investigation for the Takarazuka landslide and the previous undrained loading ring shear test for the Sale landslide suggested that the high mobility of the Takarazuka landslide was caused by the undrained loading onto the saturated layer. The sliding surface was formed inside the saturated layer below the ground surface, and the landslide mass moved scraping the surface soil layer above the saturated layer.