Tectonic setting in the study area. (a) Tectonic plates around the Japanese Islands. EU, Eurasian plate; PHS, Philippine Sea plate; PAC, Pacific plate. (b) Geological map of the ICZ modified from Geological Survey of Japan (2003) showing locations of the northwestern (this paper), western (Arai et al. 2013), and eastern (Sato et al. 2005; Arai et al. 2009) profiles. ISTL, Itoigawa-Shizuoka Tectonic Line; SIF, Shimotsuburai-Ichinose Fault; SHF, Sone Hills Fault; TATL, Tonoki-Aikawa Tectonic Line; KF, Kan'nawa Fault; KMF, Kozu-Matsuda Fault; KGC, Kofu granitic complex; TPC, Tanzawa plutonic complex. The relative plate motion between the PHS and the EU (black arrow) is from Seno et al. (1993).