Fig. 7.

Cumulative number and Z-value plots for anomalous areas detected in Fig. 5. (a) Distribution of epicenters in the volumes of Anomaly 1 (A1, blue dots), Anomaly 2 (A2, open red circles), and Anomaly 3 (A3, gray dots). Plusses denote the centers of resolution circle in each area. A black star indicates the epicenter of the 2008 Ibaraki-oki earthquake (M 7.0). A blue star indicates the epicenter of an earthquake (M 6.0) which occurred on 23 July, 2005. (b) Vertical cross-section of the east-west direction in Fig. 7(a) with the upper boundary of the Pacific plate (solid line) and the Philippine Sea plate (broken line). (c), (d) and (e) show the cumulative number (black line) and the Z-value (blue line) in the volumes of Anomalies 1 to 3.