著者

吾妻 崇 太田 陽子 小林 真弓 金 幸隆

出版者

公益社団法人 日本地理学会

雑誌

地理学評論. Ser. A (ISSN:00167444)

巻号頁・発行日

vol.69, no.5, pp.365-379, 1996-05

参考文献数

12

被引用文献数

1

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The Nojima earthquake fault appeared along the recognized active fault in the northwestern part of Awaji Island in association with the 1995 Hyogoken-Nanbu Earthquake. This earthquake fault is dominated by right-lateral offset (max. 1.7m), with a high-angle reverse fault which has a maximum verlical displacement of 1.3m uplift on the southeastern side. We have repeated the measurement of seven profiles of the fault scarp at two areas (Hirabayashi, Ogura). The fault scarp of the Hirabayashi area (profiles 1-4) is composed of the Plio-Pleistocene Osaka Group at the base and is overlain by an unconsolidated gravel bed at the top. The Ogura area (profiles 5-7) is entirely underlain by the Plio-Pleistocene Osaka Group. The fault scarp in these two areas is characterized by an overhanging slope due to thrusting of the upthrown side. Scarp retreat at Hirabayashi occurred in association with the sudden collapse of the gravel bed and proceeded more quickly than at Ogura, where fault scarp retreat proceeded by exfoliation of the fault plane as well as partial collapse of the Osaka Group. These facts strongly indicate that the lithological control is most significant for the formation of original fault scarp as well as retreat. The retreat of fault scarp was very slow after March to June at Hirabayashi and June to July at Ogura, and proceeded more quickly than some of seismically generated normal faults.