The fluidized landslide was one of the typical features in the major slope damages due to The 2011 off the Pacific coast of Tohoku Earthquake. In many slopes mainly composed of volcanic cohesive soils with high water content, their sudden strength degradation under the strong earthquake motion caused a long-distance travelling failure. In this study, the distributions of such type of landslides around Shirakawa-city are summarized briefly, and then a case study on the typical landslide at Hanokidaira in the city is presented as well. The landslide mechanism is simulated by the dynamic elasto-plastic finite element method where the cyclic loading characteristics of the sensitive soils are numerically formulated by the UW softening model with the appropriate material parameters based on the laboratory element tests with the undisturbed soil specimens. As a result, it is confirmed that the fluidized landslide was induced by the aforementioned mechanisms in the slope.

  In order to predict the landslide velocity, mass system model composed of damper is an effective method which is based on kinematic equations. Furthermore it is finally deduced by this method that downward forces（F）have close linear relationship to velocities（ν）. Therefore, velocities（ν）of landslides increase in response to increasing downward forces（F）. The analytical result using this technique to the Kostanjek landslide in Croatia clarified that this mass system model is effective to reproduce the variation of landslide velocity in response to the variation of groundwater level.