芦屋断層帯の第四紀後期の活動性

概要

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The Ashiya fault, one of the main faults of the Rokko-Awaji fault zone, central Japan, has been considered as an inactive fault during the late Quaternary (Nakata et al., 1996 ; Suzuki et al., 1996). An outcrop of the Ashiya fault showing the activity during recent 30,000 y, however, was found at a construction site, on the northern side of Sakasegawa-river, Takarazuka City. The deposits at this outcrop consist of unconsolidated sand and gravel beds with thin layers of silt and clay, which were offset at least 5 m in vertical.The radiocarbon dating and pollen analysis show that the deposits had been formed since 33,780 y.B.P. which can be compared with that of Tenma formation distributed in the area around the Osaka basin. Detailed observations and sketches show that there are at least five seismic faulting events since about 30,000 y.B.P.
日本地質学会の論文
1999-03-15