Fig. 12

Hypocenter distribution of earthquakes in the crust of the Philippine Sea plate under western Japan. Events 0–10 km below the upper plate surface are shown as red dots. Bold arrows denote estimated locations of the upper-plane seismic belt. The contact zone between the Philippine Sea and Pacific plates beneath Kanto is indicated by thick broken curves. Solid curves, red triangles, and orange curves denote iso-depth contours of the upper plate surface, active volcanoes, and source areas of large interplate earthquakes, respectively. Thick, broken gray line shows the Kyushu–Palau Ridge and its northeastern prolongation on top of the Philippine Sea slab. The northward bend near the northern end appears because of the projection of the slab’s top surface with an increasing subduction angle relative to Earth’s surface. (After Hasegawa et al. 2010)