Fig. 4.

WNW-ESE vertical cross sections of V _p perturbation and V _p /V _s beneath the Tohoku region. Black dots denote the hypocenters used for seismic tomography within 20 km of the cross section. Blue lines show the upper boundary of the Pacific plate. Large stars in B–B′ and H–H′ show the hypocenter of the 2011 Tohoku Earthquake determined by JMA. Small star in G–G′ denotes the hypocenter of the aftershock off Ibaraki. Circle in D–D′ corresponds to the relatively large slip zone estimated by Honda et al. (2011). Arrows in the upper panels of D–D′ and E–E′ denote the location of convex configuration of seafloor found. Arrows in the lower panels of A–A′ to E–E′ show the low-V oceanic crust.