Supplementary study of the Katata fault on the west coast of Lake Biwa and sublacustrine faults off Imazu to Takashima, Shiga Prefecture

Authors: Kiyohide Mizuno and Taku Komatsubara

Abstract: The study of the Biwako-seigan active fault system along the west coast of Lake Biwa in Shiga Prefecture was carried out in the three years from 1995 to 1997. However, the age of the last rupturing of the Katata fault, a south segment of the fault system, could not be clarified. Sublacustrine faults in the western part of Lake Biwa also have not been sufficiently investigated. This paper presents results of the supplementary study of the Katata and sublacustrine faults in 1998. The boring was conducted at six sites across the Katata fault, near Mano, Otsu City. Slight deformation of the Holocene deposits has been detected and a faulting event between about 5000 and 2000 14C y BP is inferred from the difference in deformation degree between the under- and overlying deposits. The rupture on the Katata fault during the 1662 Kanbun earthquake has not been proved. As a result of the sonic prospecting, sublacustrine active faults were not found off Imazu to Takashima, where sublacustrine terrace scarps are covered by sediments intercalating the Kikai-Akahoya ash (ca.7 ka).

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