足柄・丹沢地域における防災科学技術研究所反射法地震探査90-AS,91-TANデータの再解析

概要

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National Institute for Earth Science and Disaster Prevention (NIED) carried out seismic reflection surveys across the Kozu-Matsuda fault in 1990 FY, and the Kannawa fault system in 1991 FY, both of which form the boundary between the Philippine Sea and the Eurasian plates. The former survey produced the 90-AS profile, and the latter 91-TAN profile. Neither original profiles provide clear images of the Kozu-Matsuda fault and the Kannawa fault system. However, the recent processing technique makes it possible to improve the imaging of 90-AS and 91-TAN profiles. New 90-AS profile reveals that five E-dipping near-surface reverse faults may be spraying from a single low-angle thrust at depth, and that the Kozu-Matsuda fault is the highest-angle fault among the near-surface faults. The new 91-TAN profile indicates that the Kannawa thrust is dipping north- ward down to at least several km deep.