マス・ムーブメントの地質構造規制  [in Japanese] Structural Control of Mass Movement  [in Japanese]

It is clear that mass movements show different type of structural control depending on geologic systems or lithologies. Examples from Tertiary, Mesozoic, granitic area, cristalline schists, volcanic rocks, and so on show this evidently. In order to analyse the geologic control of mass movement, the following points of view concerning the geomorhic aspects of the phenomenon are important :a) We have to recognize at first that the mass movement which brings landform evolution is one of the present day geologic processes. b) Initiation of mass movement is related to some layered structures under the land surface which are often produced in relation to the particular geologic situations. c) we have to be sensitive at geomorphic expression of geologic structures to understand this relation. Questa topography due to lithology and altitude of layered rock, and fault valley due to particular hydrological and soil mechanical situation along a fault are representatives of such structural reliefs. d) Detailed geologic survey in cooperation with aerial photo interpretation is appreciated to clarify this kind of structural relief. e) Instabilizing factor like under-cutting or down-cutting of slope by river of by artificial work should be detected to understand the individual case of mass movement. It is of course true that frequency of mass movement in geologic time is controlled by climatic condition and by crustal movement during the Quaternary age. In addition, artificial change of landform is now concerning widely the occurrence of mass movement today. Even in such a case, analysis of mass movement from the view-point stated above is effective to understand the individual situation associated with slope stability.