2009 Volume 2009 Issue 31 Pages 27-32
The Kikukawa fault zone, more than 44 km long, in the western part of Yamaguchi Prefecture, is composed of the Kikukawa fault and the Kanda-misaki-oki fault. The Kikukawa fault zone is active and inferred that it has a potential of future earthquake, but its magnitude cannot be deduced because its northwestern end is not known yet. In this study, the seafloor swath mapping was conducted to determine the northwestern extension of the Kanda-misaki-oki fault. A pull-apart basin and a fault valley caused by the activity of the Kanda-misaki-oki fault were found on the survey map and the Kanda-misaki-oki fault extends further northwest. Because these structures show no trace of marine and/or fluvial erosion, these structures have been formed after the submergence around 15,000 years ago.
