Counts of occurrence per depth in 宗谷地方・宗谷海峡

Counts of occurrence per depth in 宗谷地方・宗谷海峡 (Soya region & Soya Strait) is shown as below graph,

note : There are not included of all depth to avoid too complicated curves.

• 1km(red)…This count of the earthquakes is the most one. But, the max Magnitude is only M5.6 since 1932 (The max of it in this area is M6.1 of 340km/350km in 1951/1992). The counts had have been increased rapidly after the long silent terms of it. The longest one was between 1993/2008, and the rapid increase count of 1km/10km was occurred in 2009 (next year of the end of the longest silent term). The rapid increase of the count of 10km was also occurred with it of 1km in 2022. 10km's rapid increase had been started just before 1km's one. It seems to show the tendency of the bringing the earthquake energy to shallower depth. 
• 10km(yellow)…The count is the 2nd. In 2022 increase, the curve approached to the one of 1km. The max Magnitude of 10km is M5.4 in 2022. The count increase of 1km/10km was occurred by this M5.4.
• 20km(orange)…The count is the 3rd now. The longest silent term is between 1919-1998 (Japan Meteorological Agency had started the observation of earthquakes in 1919).  The curve crossed over 1km's one between 2000-2010, and 2curves were overtaking and being overtaken after it until M5.4(10km) in 2022.
• 30km(yellow green) …The count is 4th. But, the increase has stopped since 2016. After it, the longest silent term has become about 9 years. It may be the sign of the next big earthquake or the continuous earthquakes.
• 40km(green)…The occurrence was only M4.3 in 1978.
• 320km(gray)…The count is 5th. Even though the count is only 6, the max Magnitude is M5.9. 
• 330km/340km/350km(gray)…The counts are 1-4. The max Magnitude are M6.0/M6.1. M6.1(340km/350km) is the max value in this area.