あ　と　が　き
（前略）まとめると以下のようになる．
１　調査地域において，地すべり地形は頁岩・シャールスタインの分布域で多く，砂岩・チャート・石灰岩の分布域では非常に少ない．
２　本地域には広くメランジェとみられる岩相が分布し，その中で異地性岩塊と基質の頁岩との不連続面で発生した地すべりが多いと考えられる．
３　本地域の地すべりは層理面の傾斜方向と同方向に移動している（つまり層理面がその地の地形面に沿う順層斜面において発生した）流れ盤タイプのものがそのほとんどを占め，地すべりの発生が層理面に規制されていることを示すと考えられる．これは言い替えれば，地層面という岩質の違いによる不連続面で地すべりが起こり易いことを示していると考えられる．
４　向斜ないし背斜状構造の両翼で地すべりが多発しており，褶曲に伴う岩盤の強度の劣化および風化の促進などによって地すべりが誘発されたものと考えられる．
５　調査地域では断層破砕帯での地すべりの発生が著しい．また，西北西−東南東方向のトレースを持つ浦山断層沿いに地すべりが多発しており，断層の走向が地層の走向に近い場合に地すべりが起こり易くなる可能性が考えられる．

図4．地すべり地形の分布と岩相および地質構造の関係を示す図． 　　　地層境界線，断層および背斜・向斜軸を示した．

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Distribution of the landslide configurations in the Chichibu Paleo-Mesozoic area
of east Chichibu district,with reference to lithology and geologic structure

Atsushi ISHII and Osamu TAKAHASHI
Department of Astronomy and Earth sciences. Tokyo Gakugei University. Tokyo 184, Japan.
and
Kyoko HASHIMOTO
Kyoto Kagaku co. Ltd. Kanda Sudacho 2-6-5. Chiyoda-ku. Tokyo 101, Japan.

Abstract Distribution of the old landslide that slipped in the geologic times, probably Pleistocene, and remained in configurations now was studied in Chichibu City, Yokoze Town, Arakawa and Naguri Villages. The Chichibu Paleo-Mesozoic System is distributed in the area.
This study has led the following conclusions:
1. Landslide configurations are found distributed unevenly in the studied area. They occurred often in shale and schalstein and rarely in limestone, chert and sandstone.
2. In some cases, landslides glided on the discontinuous surface between the exotic blocks and the matrix of melange.
3. There are important relationships among landslides, the direction of the slope and the direction of the dip of the strata.That is, landslides occur easily on the slope where the strata dip to the same direction as the slope.
4. Landslides were often observed also on the limbs of the anticlines and the synclines. The strata were deformed and sheared, and were lowered in competence there.
5. In the studied area, landslide configurations are concentrated on the sheared zone of the Urayama Fault. The Fault runs to almost the same direction as the strike of the strata there.
6. In planning a large civil engineering work in the area,it is very important to take into account the geological conditions where there are many landslide configurations.