北海道東部, 網走・北見・津別地域における地すべり地形の特徴と最近の地すべり災害 Characteristics of Landslide Landforms and Recent Landslide Disasters in the Abashiri-Kitami-Tsubetsu Area, Eastern Hokkaido, Japan

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空中写真から1, 765箇所の地すべり地形を判読し, それらの分布, 規模, 形態や地塊の滑動方向の特徴, 地形・地質との関係, 最近滑動し災害をもたらした地すべりとの関係を解析した。地すべり地形の約79%は第三紀泥質岩からなる地域に, そして約16%は "緑色岩類" 地域に分布する。また, 第四紀火砕物地域や火山岩地域にも点在する。地すべり地形の規模や形態, 地塊の滑動方向などの特徴は各地質域での地形, 地質構成岩の岩質・岩相や地質構造を反映している。最近発生した地すべりには地すべり地形を示す斜面が融雪, 豪雨, 地震や斜面末端開削に伴って再滑動した事例があり, 地すべり防災上, 地すべり地形の存在や特徴を知ることが重要である。

In the Abashiri-Kitami-Tsubetsu area, totally 1, 765 landslide landforms were identified through aerial photographs of which 290 (16.4 %) were found in the Mesozoic area, 1, 388 (78.6 %) in the Tertiary area, 37 (2.1 %) in the Quaternary pyroclastic area, and 50 (2.8 %) in the volcanic area.<BR>In the Mesozoic area, most landslide landsforms are found sporadically in the area consisting of Jurassic to Cretaceous "green rocks, " and most of them are small-scale debris-slumps (A type), debris-slides (F type) or debris-flows (G type).<BR>In the Tertiary area, most landslide landforms are found concentrically in the area underlain by Oligocene to Miocene strata. They consist mainly of alternating beds of shale and soft siltstone, and contain intercalated tuff beds, and are featured by prevalence of folding structures associated with faults. Most of them are small-scale debris-slumps or debris-slides. Moreover, also recognized are large-scale rock-slumps (B type) and rock-slides (E type), both of which are found along faults and/or axes of folds. More than 60 percent of landslide landforms is dip slope slide type.<BR>In the pyroclastic area, small-scale debris-slides are found sporadically on the steep slopes which are composed of sand and gravel, and the overlying pyroclastic flow deposits.<BR>In the volcanic area, some large-scale rock-slump is found at the margins of Quaternary subaerial lavas, forming a cap rock structure.<BR>In the Abashiri-Kitami-Tsubetsu area, the distribution, sizes and shapes of landslide landforms, and directions of landslide mass movement reflect landforms and geological conditions, such as lithology, lithofacies and geologic structures of bedrock geology.<BR>Some recent landslide disaster was caused by partial or entire removal of older loose landslide mass, triggered by natural factors, such as thaw, heavy rain and earthquake, and artifical factors. Therefore, much attention should be paid to presence of landslide landforms from the viewpoint of landslide damage prevention.

収録刊行物

  • 地すべり

    地すべり 32(2), 32-40, 1995-09-15

    The Japan Landslide Society

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各種コード

  • NII論文ID(NAID)
    10013869806
  • NII書誌ID(NCID)
    AN00332562
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    02852926
  • データ提供元
    CJP書誌  CJP引用  J-STAGE 
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