Geological Zonation of Landslides in Japan

Abstract

Geological zonation of landslides in very small scales was proposed based on major engineering geological division of Japanese Islands. In this paper, the term “landslides” involves all kinds of ground movements appeared in Japan. In the course of zoning works, the following problems are piscussed, namely; geomorphological development related to landforms which are controlled by lithological characteristics and types of landslides, recent crustal movements affecting the cause of landsliding phenomena, distribution density of landslides in narrower sense, etc.As results, fifteen map units are defined with explanatory table of topographic, lithological, tectonic geological features, principal types of movements, possibilities of prediction and foreknowledge, planning of controll works. Also, typical geological cross sections are illustrated for each map units.Map units represented in the zonation map are as follows:1) Acidic intrusive rocks and gneisses2) Ultramafic and mafic intrusive rocks3) Paleozoic-Early Mesozoic eugeosynclinal deposits, crystalline schist facies4) Paleozoic-Early Mesozoic eugeosynclinal deposits, non-metamorphosed facies5) Cretaceous marine deposits of turbidite facies6) Late Mesozoic-Paleogene eugeosynclinal and flysh-type deposits7) Late Mesozoic-Paleogene terrestrial volcanic rocks8) Tertiary non-marine to neritic deposits9) Miocene submarine volcanic rocks10) Middle Miocene-Pliocene marine clastic sediments11) Pliocene-Pleistocene terrestrial volcanic rocks12) Quaternary terrestrial and neritic clastic sediments13) Quaternary pyroclastic rocks and sediments14) Quaternary volcanic rocks15) Late pleistocene-Holocene clastic sediments