Fig. 1
From: Deep subduction of the Philippine Sea slab and formation of slab window beneath central Japan
Tectonic setting in southwest Japan. a Map of the tectonic setting of the southwestern Japanese islands. Red lines represent the depth contours of the upper surface of the PHS slab. The geometry of the PHS slab (Hirose et al. 2008; Hua et al. 2018) has been determined by integrating the results of various recent seismic analyses (Hirose et al. 2008; Nakajima et al. 2009; Zhao et al. 2012; Huang et al. 2013; Asamori and Zhao 2015; Liu and Zhao 2016; Hua et al. 2018). The iso-depth contours are provided at a 10-km interval for the shallow section (~ 150 km) and a 30-km interval for the deep section (> 150 km). The thin dotted blue lines represent the subducting PAC slab to 250 km depth at every 50-km interval (Nakajima and Hasegawa 2006). The shaded red zone represents the contact zone of the PHS and PAC slabs (Nakajima et al. 2009). Dashed black lines represent trenches and troughs. Bold dashed blue lines represent the locations of the extinct Kinan seamount chain and the Kyushu–Palau ridge. Black triangles represent volcanoes. b Location names in the study area (same area as in a) that are mentioned in the text. The inset map shows the location of the study region