EARTHQUAKE sOIL ROOK FLOW IN NAGANO IN JAPAN

The earthquake of 14 Sep. 1984 in west Nagano caused massive soil rock flow. The castic detritus and rock debris containing volcano ashes on the steep slope of Ontake mountair and topography with u narrow, long and sharp river valley Provided necessary condition for soil rock flow. The earthquake induced slipping and collapsing of the porous clastic detritus on the steep slope of Ontake mountain. The raining before and after the shock promoted the occurence of slipping and collapsing and led to the soil rock flow.