Figure 7: Mantle wedge tomography across Honshu, Japan, after Zhao et al. (1992). Earthquake loci are projected as small open circles, relative mantle Pwave velocities are shown in colors, from red (slow) to blue (fast). Note that there are two parallel zones of earthquakes, with the upper one defining the upper part of the plate. Note that the zone of “slow” mantle, inferred to reflect partially molten zones, lie several tens of km above the subducted slab.