Middle Pleistocene fluvial terrace and reconsideration of the activity of Tachikawa fault zone, Musashino upland, central Japan

Abstract

The Kaneko and Tokorozawa fluvial terraces are distributed in the northwest Musashino upland, central Japan. Recent studies concluded that they were formed during marine isotope stage (MIS) 6. In this study, we identified Iz-NY and hpm1 tephras in the basal part of overbank and aeolian deposits covering the Kaneko and Tokorozawa fluvial terraces. Based on ages of Iz-NY and hpm1, we indicated that the Kaneko and Tokorozawa fluvial terraces were formed during MIS 7. Then, the vertical slip rate of the Tachikawa fault displacing Kaneko fluvial terrace is reestimated at 0.03-0.04 m/ky, showing a lower slip rate.