Characterization of terrain surface and mechanisms of shallow landsliding in upper Kurokawa watershed, Mt Aso, western Japan

Abstract

The paper describes the physical characteristics of the Mt Aso caldera (western Japan) where some 959 shallow landslides occurred between 1990 and 1998, denuding an area of 0.638 km2. The variation in type and thickness of the recent pyroclastic deposits are described and linked to the spatial distribution of the landslides. The high monsoonal rainfall in July 1990 percolating into the recently deposited tephra overlying less permeable bedrock first saturated the soil mass and then effectively ‘floated’ the low density pyroclastic materials such that many slips occurred in the small, actively eroding, tributary valleys.