Abstract
The Nebukawa-station Landslide was triggered by the Kanto earthquake in 1923. Both geological and geotechnical studies point out that the landslide failed rapidly by shearing (compression failure) in the weak pumice layer which was accompanied with the unique deformation named “squeezing-out” that is, the upper layer, mainly massive lava flow, subsided and squeezed out the underlying pumice layer to the front of slide, and the slope collapsed successively.
The elastic-plastic FEM analyses both on the landslide and the simplified three-layers model indicate that the “squeezing-out” is one of the common deformation type on slope which consists of thin weak intertrappean layer (e. g. pumice) and gentle dipping (less than 10 degree) thick rigid layers (e. g. lava).
Several geologic evidences support the idea that the landslide with the “squeezing-out” deformation occurs in dissected slope of stratovolcano, and sometimes leads to the run-off of debris, high speed and long distance; these will then provide basic information useful for disaster prevention planning.
