Regional distribution of large landslide landforms in Japan

Abstract

Distribution map of large landslide landforms (longer than 200m) on whole Japanese islands was compliled by using landslide maps (mainly 1: 50, 000 scale) and detection of 1: 25, 000 scale topographical maps. The landslide landforms are widely distributed on Japanese hills and mountains, especially in the back arc zone of Tohoku district, Shin-etsu, Hokuriku and Shikoku districts. Relationships between regional distribution of landslide landforms and geological and topographical features are analyzed by GIS (Geographical Information System) over the Japanese islands. Data on landslide landforms, geology, relief energy and slope gradi-ent were prepared with 2 x 2km mesh system. The number of meshes for statistical analyses is about 71, 000. Landslide landform exists in 43% of portion among these meshes. In 2602 meshes (3.7% of total meshes), landslide landforms cover more than 40% of each mesh area.The landslide landforms are densely distributed in the Neogene sedimentary rocks, Green Tuff and the Paleogene and Neogene coalfields. Relative high dense distribution of landslide landforms are observed in the mountaineous region with 400-800m of relief energy and 15°-30° of slope gradient. The landslide landforms are scarcely distributed in the areas with dispersion of altitude more than 120m or less than 30m.