Geological origin of large-scale landslide topography in the Higashinaruse region of Akita Prefecture, northeast Japan

Abstract

Mountain slopes of landslide origin are distributed under the 25km² in the Higashinaruse regeon, Akita Prefecture, northeast Japan, where the Neogene siliceous mudstone are dominant. We have studied the formative process of such landslides through investigating geological structures and rock fractures in the siliceous mudstone in the field. As a result, it has been clarified that such large-scale landslide topography was not formed by a single block movement but has been formed in multi blocks. The topography of these landslide blocks have been formed under control of the fractures of siliceous mudstone and the inclination direction of the stratum. These results are expected to clarify the mechanisms of landslide formation in the Neogene siliceous mudstone beds that are widely distributed in northeast Japan.