Counts of occurrence per depth in 根室地方北部

Counts of occurrence per depth in 根室地方北部 (North Nemuro region) is shown as below graph,  

• 1km (red)…This count of the earthquakes is the 1st one. There was a continuing earthquakes in 2004. But , there was no major earthquake except M4.8. This M4.8 is the max magnitude in 1km. Before these earthquakes, there was the longest silent term between 1964-2002. The curve is still glowing actively. 
• 10km (yellow)…This count is the 2nd. The curve was overtook by 1km's continuing earthquakes in 2004. Before it, there were the 1st & 2nd longest silent terms except 1919-1931 (no earthquake record of 10km). These terms overlapped with the one of 1km. The max magnitude of 10km is M5.3 in 1963.
• 120km/130km/140km(gray)…These counts are the 3rd. The each max magnitude is M5.1 in 1955 & in 2006/M5.8 in 2007/M4.8 in 1967. The max magnitude for all depths is M6.1 of 160km. 160km has only 2 times earthquakes.
• Others… omitted.