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.

著者

八反地 剛 森脇 寛

出版者

The Japan Landslide Society

雑誌

日本地すべり学会誌 : 地すべり = Journal of the Japan Landslide Society : landslides (ISSN:13483986)

巻号頁・発行日

vol.48, no.1, pp.45-51, 2011-01-25

参考文献数

21

被引用文献数

3

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神奈川県・静岡県の丹沢地域および箱根地域の地すべり地形分布図を用いて地すべり斜面の地形解析を行ない, 各地域の等価摩擦係数 (以下H/Lとする) , 土塊の拡散性の違いについて議論した。いずれの地域においても, 地すべりの規模 (発生域の面積) とH/Lの関係は不明瞭で, H/Lは発生域の斜面勾配に比例する傾向が明瞭であった。また, 箱根地域における斜面勾配とH/Lの比例関係から得られたH/Lの予測下限値が, 箱根地域で発生した早雲山地すべりのH/Lの実測値とよく一致し, 地すべり地形分布図から得られるH/Lの予測下限値の有用性を確認した。地すべり地形斜面の発生域と流下堆積域を含む全体の面積と発生域の面積の比 (土塊拡散率) は多くの地すべりで1. 0から2. 0の範囲にあったが, 箱根地域では2. 0を超える地すべりが3例あった。箱根地域は丹沢地域に比べてH/Lが小さくなりやすく土塊拡散率が高いことから, 地すべり災害が発生した場合被害が拡大しやすいことが予想される。

著者

佐藤 昌人 八反地 剛 松岡 憲知

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.125, no.1, pp.133-153, 2016-02-25 (Released:2016-03-22)

参考文献数

168

被引用文献数

4 3

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Weathering processes on Martian surface are among the essential issues for both understanding landform evolution and exploring water availability on Martian surface. Studies are reviewed on various weathering processes on Martian surface based on images, data collected by rovers, and laboratory approaches. Recent explorations by the Mars Exploration Rovers reveal that chemical weathering occurs on the surface of basaltic regolith. Dissolution of olivine and oxidation of Fe produces weathering rinds on basaltic surface regolith. Rock interiors also show vugs and veins filled with light-toned efflorescence indicative of chemical weathering. In particular, in high-latitude areas the two Viking landers and the Mars Pathfinder observed honeycomb weathering, angular rock fragments, and polygonal cracks in bedrock. Most of these features are also observed in the Antarctica and other cold deserts on Earth, and are generally attributed to physical weathering such as salt crystallization, thermal weathering, and/or frost weathering. Some studies successfully estimate periods and rates of weathering on the Martian surface, which promote a further understanding of environmental changes and landform evolution.