Paleoseismological study of the Daguchi fault in Fukui Prefecture

Authors: Yuichi Sugiyama and Toshikazu Yoshioka

Abstract: The Daguchi fault is a 9 km-long NE-SW-trending fault in the mountainous area on the north of Lake Biwa, central Japan. Our trench survey has revealed that its most recent activity occurred between the 15th and 17th century. The vertical displacement associated with the last rupture is estimated at nearly 1 m (1.5 m at the maximum) on the basis of measurement of fault scarps still remaining in the mountains. The penultimate event about 5-8 ka is inferred from an intercalation of scarp-derived colluvial deposits between humic layers deposited in swamp at the foot of the fault scarp. The average vertical slip rate is estimated to be around 0.15 m/ky based on 4-meters vertical displacement of the terrace gravels ca. 25 ka. The mean recurrence interval of the fault is therefore calculated at around 6-7 ky.

Index map