Fig. 5.

Comparison of the final hypocenter distribution determined by the OBS networks to the hypocenter distribution before the mainshock and slip distribution during the mainshock using strong motion data (Yoshida et al., 2011). Long-term OBS data from 2004 to 2008 were used to obtain the hypocenter distribution before the mainshock. The inverted red triangles indicate the positions of the pop-up-type OBSs for the aftershock observation. The circles filled with color represent the hypocenters of aftershocks. Grey circles indicate the hypocenters of earthquakes before the mainshock. The thick line indicates the profile of the seismic survey. Red contours indicate depths of surface of the subducting Pacific plate by marine observations. (a) For the northern region. (b) For the southern region. (c) Comparison of the hypocenter distribution between the aftershocks and earthquakes before the mainshock by the OBS data for the northern region. Depth profiles along the east-west direction are shown. Red line indicates the position of the plate boundary.