The α track etch method, which is one of the geochemical survey methods for the mapping and detection of active faults and the evaluation of their activities, has been applied to the Kannawa and Kozu-Matsuda fault areas for the purpose of the study of active faults.
The method conventionally measures relative radon concentration in the soil gas by counting the track density (tracks/cm²·day) recorded on a small piece of plastic film (cellulose nitrate) which is sensitive to α-ray radiation.
As the result of the track measurement on survey lines crossing the Kannawa fault and the younger fault which cuts the former at Yumotodaira, the town of Yamakita, Kanagawa Prefecture, it was clarified that the peak in the track density appeared just above the points on the both fault lines which were shown by HOSHINO and HASE (1977).
As the results of the track measurement on the survey lines K at the vicinity of the Kamonomiya tunnel on Shinkansen, Japanese National Railways and S₁, S₂, and S₃ at Sogodai, the town of Ohi, Kanagawa Prefecture, crossing the Kozu-Matsuda fault system, the following was clarified:
1. A group of several peaks in the track density at the western segment of survey lines S₁ and S₂ corresponds, to“a”fault of the Kozu-Matsuda fault system which was shown by Research Group for Active Faults (1980).
2. A group of several peaks in the track density at the eastern segment of the survey line S₂ corresponds to the eastern fault in parallel with“a”fault of the Kozu-Matsuda fault system.
3. Because there are many peaks in the track density on the survey lines S₁ and S₂, it is supposed that there exists a wide fault fracture zone under the Sogodai hill.
4. Some peaks in the track density on the survey line K correspond to“d”fault of the Kozu-Matsuda fault system.
5. Considerable difference in the track density between“a”and“d”faults may suggest the difference in the activity of both faults.

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仙台の青葉東断層は双葉破砕帯の再活動によって生じた南北走向の左横ずれ断層である.青葉東断層を南方に追跡し,青葉東断層は阿武隈川南岸の双葉断層の延長であることを確認した.この結果,双葉破砕帯は北方に20km追加された.青葉東断層,坪沼断層,長町-利府断層,久の浜-岩沼撓曲は段丘や愛島火山灰を切断・変形させており,いずれも第四紀の東西あるいは北西-南東の圧縮応力場で形成された活断層・活撓曲である.坪沼断層と長町-利府断層は互いに延長されず,青葉東断層で分断されている.

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神奈川県西部から静岡県東部にかけての地域は，伊豆弧と本州弧の衝突帯に位置し，様々な活構造が分布する．特に神縄断層や国府津-松田断層，およびそれら断層によって分布を規制される更新統の足柄層群については，伊豆弧衝突の最前線として，島弧衝突帯のテクトニクスに関する様々な研究成果が報告されてきた．近年，大規模な地下構造探査プロジェクトにより，この地域のプレート構造について新たな知見が得られ，再び注目を集めている．本見学旅行では，本地域に分布する活断層の露頭や足柄層群に挟在される火砕流堆積物を見学し，本地域の衝突テクトニクスに関して議論する．

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The Sakawa river, 45km long,flows from Mt. Fuji down to the Sagami Bay. The lower reaches of this river forms the Ashigara alluvial plain. There exist two kinds of Recent terraces in the plain. The author conducted a geomorphological survey of the distribution and the structure of these Recent terraces in order to show that the formation of an alluvial plain can be affected by volcanic activity and crustal movement. The greater part of the plain is occupied by a fan which was formed by the Sagami river. In addition, there are many small scale landforms such as sand dunes along the shoreline, small fans by the Oiso hill, and valley plains at the foot of Mt. Hakone (Fig. 2 ). The Recent terrace I surface, which is distributed fragmentarily in the gorge of the middle reaches and stands about 30m above the present river bed, corresponds to the Gotenba volcanic mudflow surface at the foot of Mt. Fuji. According to Machida, the volcanic mudflow occurred about 2, 300 years ago. In the Ashigara plain the distribution of the Recent terrace I surface is limited to the fringe of the Sekimoto hill and Mt. Hakone. The relative height of the terrace cliff between the Recent terrace I surface and the present river bed decreases rapidly towards the lower reaches of the plain: 25m at the lower exit of the gorge, 10m at Komagata-Shinjuku, 2m at Numata and so on. Consequently, the Recent terrace I surface is underlain by the present river bed. The Recent terrace II surface is either erosional surface or contemporaneous depositionl surface. Erosional surface is distributed in the gorge and about 10m lower than the terrace I surface. Depositional surface is preserved broadly around Kamonomiya on the left bank along the lower reaches in the plain. The terrace cliff of the II surface increases progressively from O. 5m at Nobukiyo to 4m near the seashore in its height (Fig. 3 , 4). The deposits constituting the Recent terrace I surface are basaltic sand and gravel. Most of the gravels are sub-angular, and laminae are well preserved in the bed. It is considered that these deposits were formed by rapid deposition of short duration. On the other hand, deposits constituting the Recent terrace II surface in the plain can be classified into three beds, Iower C_2, S, and upper C_3. The C_2 bed consists of clay, silt and humus. The S bed consists of the basaltic sands O. 5 to 3. 5m in thickness. The C_3 bed consists of clay, silt and sand with irregular thickness. The C_3 bed forms the present micro-relief of the ground (Fig. 5 ) (Tab. I ). The Recent terrace H around Kamonomiya is uplifted by the crustal movement. The amount of uplift becomes larger to the south and the west. It is considered that an uplift has amounted to ovcr 3m since 2, 300 years when the basaltic sand which corresponds to the Gotenba volcanic mudflow was deposited.

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国府津・松田断層の地震テクトニクス上の位置づけに関しては,現在二つの異なる見解が示されている.一つは,相模トラフ内のセグメントとは独立に活動し,丹沢山地や大磯丘陵を持ち上げる大磯型地震を引き起こすというものである.もう一つは,関東地震を200～300年ごとに引き起こすプレート境界断層から分岐した副断層の一つであり,関東地震と連動することなしに大地震を起こすことはないという考えである.これを検証するため,断層崖の麓で5個所のトレンチ発掘調査を行い,最新の断層活動史を復元した.完新統に明瞭な断層変位は認められなかったが,地辷りや崩壊堆積物から3,000年間に4ないし5回のイベントが識別された.このうち,大規模なイベントは約3,000年前の1回だけで,これが同断層の活動を示すと考えられる.ほかの小規模なイベントは,相模トラフで発生した大地震の可能性があるが,その頻度は数百年という短い間隔ではない.

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　地震観測に基づく都市ガス供給遮断システムを「k-out-of-n遮断システム」と定義し，東北地方太平洋沖地震における第1次緊急停止判断を事例として，観測SI値とブロック供給遮断確率の関係を表す機能的フラジリティ関数を，対数ロジスティック分布を用いて構築するとともに，k-out-of-4遮断システム(k=1, 2, 3, 4) とした場合の結果の相互比較を通じて，そのシステム特性を明らかにした．またリサンプリングを復元抽出・非復元抽出としたbootstrap法により，仮想的な k-out-of-n遮断システムを多数生成して供給停止シミュレーションを行った．供給停止割合の平均値と標準偏差の比較を通じて，多様なシステム形態および地震観測体制の下での運用方法について有用な知見が得られた．

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