地震 第2輯
Online ISSN : 1883-9029
Print ISSN : 0037-1114
論説
糸魚川-静岡構造線活断層系中北部で新たに得られた活動時期
谷口 薫渡辺 満久鈴木 康弘澤 祥
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ジャーナル フリー

2011 年 64 巻 1 号 p. 11-21

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The 150 km long Itoigawa-Shizuoka Tectonic Line Active Fault System (ISTL) in central Japan is one of the most active fault systems in Japan. Paleoseismologcal studies 1980s have revealed that the most recent event and the average recurence interval of the ISTL. The approximately 7 km long portion of the fault system between Matsumoto and Okaya has been regarded as a gap without any active fault trace. The gap namely the “Shiojiri Pass Gap” has long been taken as a segment boundary owing to the geometric discontinuity. Recent geomorphological analyses of the gap have demonstrated a through-going left-lateral slip assocaited with recent earthquakes in this area, based on aerial photograph interpretation and excavation studies. Excavation study on this portion revealed that the latest faulting event occurred between 1,700 cal. B.P. to 1,310 cal. B.P. (255 A.D. -645 A.D.). The timing of the last faulting event at this study area coincides with the timing in the Gofukuji fault and Okaya fault. The active faults extending from the Matsumoto basin as far as the northwestern margin of the Suwa basin display the evidence for its recent reactivation at the same time.

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© 2011 公益社団法人 日本地震学会
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