Trenching survey of the Kitatake fault at Nobi, central Miura Peninsula, Kanto, Japan

概要

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The Kitatake fault is a right-lateral active fault running WNW to ESE, through the central part of Miura Peninsula. Although the fault located in the densely populated area, little is known about its paleoseismological records. Thus, trenching survey was performed to reveal the latest paleoseismic event at the eastern part of the Kitatake fault at Nobi, Yokosuka City. At the trench walls, the fault trending N52-42°W 35-67°S, displaced the humic mud dated at 1540±80 y. B. P. Its upper termination is covered by the channel fill dated at 1020±70 y. B. P. Thus the latest paleoseismic event associated with the Kitatake fault is estimated to be between 1540±80y. B. P. and 1020±70y. B. P. The evidence of paleo-liquifaction in the sediments suggests that this site has been suffered strong ground motions after 460±90y. B. P.