Fig. 4

Relocated hypocenters (green circles: aftershocks, white stars: mainshock) in the present study plotted on along-arc vertical cross-sections of the detailed seismic velocity structures estimated by Kita et al. (2012). Relocated hypocenters of aftershocks within 5 km from the vertical section were plotted. The locations of the sections are shown in the inset map. The thick white lines in d and j show the locations of the faults of the 1970 and 1982 events. (left) P and (right) S wave velocities are indicated by the color scale. Black dots indicate the hypocenters used in the tomographic inversions presented in Kita et al. (2012). Thick white lines delineate the upper surface of the subducting Pacific slab. Contours indicate P and S wave velocity values contoured at intervals of 0.6 and 0.3 km/s in b–f and h–l, respectively (and 0.5 and 0.25 km/s, respectively, in a, g). Green and green dashed ellipses in a and g indicate the locations of intrusion of the high-velocity materials. The bold horizontal lines at the top of each plot represent the land area. Triangles at the top of the plots indicate the locations of thrust faults (green: thrust (extension of Ishikari-teichi-toen fault zone), aqua blue: Yubari-dake fault, red: Hidaka main thrust, dark blue: Tokachi Plain faults, pink: Urahoro fault). The green and gray rectangles and the gray area at the top of the plot indicate the locations of the Hidaka and Kamuikotan metamorphic belts, respectively. White-shaded areas indicate portions of DWS < 500