Fig. 5

Vertical profiles of velocity structure and geometries of the upper boundary of the PHS. a Vertical profiles of velocity structure along the Y axis shown in Fig. 2c. b Geometries of the upper boundary of the PHS. Red and magenta lines show the depths of the upper boundary of the PHS based on the tomographic image and results by Ito et al. (2017), respectively. Blue and green dotted contours show depths of the upper boundaries of the PHS estimated by Uchida et al. (2010) and compiled by Kono et al. (2017). The location of the low-velocity anomaly in the NA plate is indicated by the black circle labeled “B.”