Fig. 4.

(a) (d) (g) (j) Red open circles are N = 150 epicenters sampled around the nodes with the high Z-value anomalies detected in Fig. 3. The location of the nodes are shown at the top of each figures, (b) (e) (h) (k) cumulative number curves (black lines) and Z-values (red lines) for the sampled epicenters, and (c) (f) (i) (l) space-time plots. A closed star indicates the epicenter of the main shock determined by JMA. The asperity ruptured by the main shock is shown in contour every 4 m of displacement on the fault (Ozawa et al., 2011).