地すべり現象に関する日本列島の地質地帯区分

The term "landslides" involves all kinds of slope movements recently distributed in Japan. The author proposed geological zonation of landslides in very small scale, based on major engineering geological division map of Japanese islands. In the course of zoning works, such engineering geological conditions as hydrogeoiogical factor, geomorphological factor and recent geodynamic phenomena are discussed concerning to primlary factors and inducing causes of landslides. Hydrogeological conditions are uniform in macroscopic view, because of large precipitation and high water table in Japanese mountainous and hilly areas. Recent geodynamic phenomena, so far as mountainous and hilly areas, is uniform because the areas are constantly uprifting throughout Quaternary period, therefore slopes usually tend to be instable state. Weathering properties, permeability, natures of discontinuities in rock masses are factors affecting landslides as primary factors, and above-mentioned engineering geological factors are considered to be represented by principal lithology of each engineering geological division. Among the characteristics, spatie distribution of open discontinuities affecting permeability and geotechnical strength are examined for each engineering geological units. As results, fifteen map units are defined, and typical cross sections are illustrated for each map units. Map units represented in the zonation map areas follows, in desecnding order; 1) Late Pleistocene-Holocene clastic sediments; 2) Quaternary volcanic rocks; 3) Quaternary pyroclastic rocks and sediments; 4) Quaternary terrestrial and neritic clastic sediments; 5) Pliocene-Pleistocene terrestrial volcanic rocks; 6) Middle Miocenc-Pliocene marine clastic sediments; 7) Miocene submarine volcanic rocks; 8) Paleogenc-Miocene non-marine to neritic deposits; 9) Late Mesozoic-Paleogene terrestrial volcanic rocks; 10) Late Mesozoic-Paleogene geosynclinal-facies and flysh-type deposits; 11) Cretaceous marine deposits of turbidite facies; 12) Paleozoic-Early Mesozoic geosynclinal-facies deposits, non-metamorphosed facies; 13) Paleozoic-Early Mesozoic geosynclinal-facies deposits, crystalline schist facies; 14) Ultramafic and mafic intrusive rocks; 15) Acidic intrusive rocks and gneisses.