C-14 ages of the low terrace (L1) deposits and surface ruptures associated with the 2008 Iwate-Miyagi Nairiku earthquake along the Mauchi River at Mochikorobashi, Ohshu City, Iwate Prefecture, northern Honshu, Japan

Abstract

We obtained C-14 ages of about 20,000 yBP from wood fragments collected within lower terrace (L1) deposits, along the Mauchi River at Mochikorobashi, Ohshu City, northern Honshu. The L1 surface at the eastern part of Mochikorobashi may indicate flexural deformation trending north-south with relative scarp height of about 13 meters. Less than 0.5 m high surface ruptures associated with the 2008 Iwate-Miyagi Nairiku earthquake (Mj:7.2, Mw:6.8) had appeared just along middle portion of this flexural slope. The average slip rate of vertical component across the Mochikorobashi flexure is estimated to be 0.65mm / yr in maximum.