Recent activities of the Shiroishi fault in the southern part of the Miyagi Prefecture, northeast Japan

Abstract

The recent activity of the Shioishi fault, northeast Japan, is investigated on the basis of the interpretations of aerial photographs, field surveys and trenching surveys. Some geomorphic surfaces show cumulative vertical offsets along the active fault. The vertical component is upthrown on the west side: 2 to 3 m on the Holocene L3 surface. The age of the most recent event could be constrained between 360 and 840 B. C. The timing of the penultimate one is bracketed to be between 9,550 yBP and 11,800 yBP. Thus, the estimated average recurrence interval is between 7 to 9.5 ky, and the ground surface has been vertically dislocated 2-3 m by single reverse slip.