Fig. 3

Relationship between focal depth and year of occurrence of large earthquakes for each century that occurred during 1500–2000. Data is obtained from ROMPLUS catalog (Oncescu et al., 1999). (a) M ≥ 7.0 earthquakes. The squares indicate the 1940, 1977, and 1986 earthquakes relocated in Hurukawa et al. (2008). The large solid circles and small open triangles indicate M ≥ 7.3 and 7.0 ≤ M ≤ 7.2 earthquakes, respectively. The open ellipses indicate main activities at the 3 seismic active periods and the arrows indicate the migration of seismicity from deep to shallow segments in seismic regions in each century. (b) Earthquakes with 6.0 ≤ M ≤ 6.9.