Fig. 20

Seismic velocity structure along the lower seismic plane under eastern Hokkaido. Shown are across-arc vertical cross-sections of a, c P-wave velocity and b, d S-wave velocity under eastern Hokkaido. P- and S-wave velocities along two lines in the inset map are shown by the color scales at the right. Aftershock activity of the 1993 M 7.5 Kushiro–Oki intraslab earthquake is shown by an arrow in c. Solid lines denote the upper surface of the subducting slab. Solid lines and red triangles at the top show the land area and active volcanoes, respectively. (After Nakajima et al. 2009c)