Quaternary faulting and channel migration along the Gero fault of the Atera fault belt, central Japan

Abstract

We performed a geomorphological and geological survey to clarify the detail geometry and faulting of the active fault around the Gero fault of the Atera fault belt, which is one of the prominent faults in central Japan, and also considered the channel migration around the fault. This survey area is dominated by many tectonic landforms and fault outcrops. The northwestern part of the Gero fault is characterized in the fault of middle and low dips northeast, and the fault which branches toward north. We think that these structures were formed for the overlapping strike-slip faults, namely the Gero fault and the Yugamine fault. Judging from the topography and geology around the Gero fault, we think that the Norimasa River at one time passed the neighborhood of the northern part of Nojiri district through a stream bent to left-lateral offset. Similarly, the Ogawa-tani River also was a stream bent to left-lateral offset, and passed the Hachiya-toge Pass, probably. Amounts of the bend along the fault of the restored Norimasa River and Ogawa-tani River are about 2.8 km and about 1.0-2.5 km, respectively.