Fig. 3

Results of the tomographic inversion in horizontal section. Velocity structures for P-wave (left), S-wave (middle), and V _p/V _s (right) are shown. Black triangles and squares indicate stations. White circles indicate earthquakes within 10 km from each section. Black crosses represent the locations of velocity nodes. Black bold lines indicate the location of the upper boundaries of the PAC (Nakajima et al. 2009) and PHS (Uchida et al. 2010) at each depth. The black dashed line denotes the northeastern limit of the PHS (Uchida et al. 2009). High-velocity anomalies associated with the mantle part of the PAC and PHS are indicated by “PAC” and “PHS,” respectively. The low-velocity anomaly in the NA plate is indicated by the white circle labeled “B.”