著者

木下 祐介 八反地 剛 八木 勇治 江崎 隼輝 奥村 大輔

出版者

日本地形学連合

雑誌

地形 (ISSN:03891755)

巻号頁・発行日

vol.35, no.1, pp.25-39, 2014-01-25

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The 2011 East Japan Earthquake caused landslides across the Northern Kanto and Tohoku Regions. The purpose of the present study is to reveal the characteristics of shallow landslides induced by the earthquake and subsequent rainfall in granitic mountains located in northern Ibaraki Prefecture, Japan. Total 140 shallow landslides were identified through interpretation of aerial photographs and fieldwork. Among the 140 landslides, 65 were directly triggered by the main shock (March 11 to 18, 2011), and the rest 75 were triggered by rainfall events or other earthquakes from March 19 to December 15, 2011. The most of them are shallow landslides with a slip plane of granitic soil (grus). Bedrock or weathered bedrock is exposed on some landslide scars in the area underlain by biotite granite where soil is thinner. Among the 87 landslides, which occurred on natural hillslopes, 50 landslides slid eastward (NE to SE). The bias in landslide direction on natural hillslopes would correspond to the direction of crustal movement of the main shock.