Abstract
The Triassic Nariwa Group is composed of consolidated rocks of marine to non-marine deposits. The Nariwa Landslides which have low angle slip surface with slow displacement velocity are characterized by the slip surface in a coaly bed in non-marine successions. The Nariwa Group is affected by folding and open cylindrical folded structures are formed. The aim of this paper is to study an effect of geological structure to form landslide. Detail observations of landslide distribution and analysis of the structures of landslide mass have been carried out in the Yasunari Landslide Area of Kawakami Town, Okayama Prefecture. Structural analysis of folds of the Nariwa Group is also precisely studied in this area. The landslide which distributed in the area of hinge of syncline structure was found. The direction of mass movement fits with that of fold axis of the syncline. The shape of the main slip surface is similar to the folded structure representing that the landslide is controlled by the pre-existing folded structure.
