糸魚川-静岡構造線活断層系北部・松本地域における反射法地震探査

概要

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The Itoigawa-Shizuoka tectonic line (ISTL) active fault system shows complicated fault traces in the Matsumoto area, at the southern end of the northern part of the ISTL active fault system. In this area, there are two tectonic deformation zones; the clear sinistral fault (Gofukuji fault) and the anticline and reverse fault (Akagiyama fault). To clarify the relation between the two deformation zones, we conducted two high-resolution shallow seismic reflection surveys across Gofukuji and Akagiyama faults. The lengths of the seismic line are 1.6 and 1.9km, respectively, and the receiver interval was 10m and the shot point interval was 10m (Gofukuji seismic line) or 5m (Akagiyama seismic line). In the Gofukuji seismic line, we estimated the east-dipping Gofukuji frontal thrust and possible high-angle Gofukuji fault. The Akagiyama seismic profile demonstrates an asymmetric anticline with a steeper eastern limb associated with the west-dipping Akagiyama fault. Based on the tectonic geomorphological features and subsurface structure, it is considered that the two deformation zones were formed by a single main east-dipping fault with reverse and strike-slip displacements. Through slip partitioning, the high-angle Gofukuji fault shows sinstral displacements, and Gofukuji frontal thrust and Akagiyama fault accommodate shortening deformation.
東京大学の論文
2007-08-20