Abstract
Dainenjiyama fault is a back thrust of the Nagamachi-Rifu fault forming a distinct fold (flexure) scarp across the urban district in the Sendai city, NE Japan. This paper aims to identify detail location of fault, fault feature and displacement of the Dainenjiyama fault, which are important for a disaster prevention perspective, based on the observation of fault outcrop exposed by construction and surrounding fault topography. F1 and F2 faults, displaced sand and gravel layer, are appeared on this outcrop. Accumulated displacement of the gravel layer suggests that the F1 fault has moved at least twice. The net displacement of the Dainenjiyama fault is estimated to be 0.8 m by the vertical displacement (1.6 m) and fault history of the F1 fault. The height of the fold (flexure) scarp on the Uemachi terrace is 5-6 m, which is much greater than displacement of F1 fault and F2 fault. This implies the presence of other fault in addition to these two faults. On the basis of these results, we conclude that the Dainenjiyama fault would branch into multiple in the fault scarp. Thus activity of the Dainenjiyama fault would cause surface ruptures which of triggering a serious disaster to infrastructure in the Sendai city.
