Counts of occurrence per depth in 北海道東方沖

Counts of occurrence per depth  in 北海道東方沖(East offshore Hokkaido region)  is shown as below graph,  

Many great earthquakes have been occurred in this area. More than M7 are 6 times between 1919-2024 as showed in the graph below. 50km/40km/30km are major instead of 20km/10km. 50km/40km's curves are over even 1km's one now.It seems M8 or so on could be occurred in the case of the domino effect including not only 50km/40km, but also 10km/1km/etc.

50km(light blue)…This count is the 1st. The longest silent term was between 1939-1954 from M6.6 in 1939. After it, there was both rapid increase of 50km and following 40km. Moreover, M8.1 of 10km followed them. There were some rapid increases after great earthquakes, like as M7.5(1km) in 1924, M7.8(40km) in 1969, M7.1(50km) in 1973, and M8.2(30km) in 1994. In result, the count becomes the 1st. The the largest magnitude in this depth is M7.1 in 1973. 

40km(green)…The count is the 2nd. The curves of 40km/50km have been overlapped each other since 1964. The the largest magnitude in this depth is M7.8 in 1969. 

1km(red)…The count is the 3rd. After M8.2 of 30km in 1994, 52km/40km counts had grown rapidly. But, the curve is following them still. The the largest magnitude is M7.5 in 1924. 

30km(yellow green)…The count is the 4rd. The curve almost caught up 1km after M8.2 in 1994. But it couldn't even though M8.2 of 30km is the greatest one of all depth. It seems most of M8.2 energy has been absorbed by the bot aftershocks of 50km/40km. The last occurrence was in 2019. s M6.6 in 1945.

60km(blue)…The count is the 5th. The curve is following 50km/40km with similar pattern, but far less. The the largest magnitude in this depth is M7.0 in 2000.

20km(orange)… The count is the 6th. After M7.8 of 40km in 1969, the curve almost overlapped with 50km. But, around 1990, the silent terms became longer than 50km. The the largest magnitude in this depth is M6.2 in 1969 as one of the aftershocks of M7.8 of 40km on the same day. 

10km(yellow)… The count is the 7th. On M8.1 in 1958, the count was the 2nd behind 1km. But, at this time, 40km curve had almost caught up 10km. Because of slow growing of the counts, the curve is under 20km even though M8.1 of 10km in 1958 is the 2nd greatest one of all depths.  

others…omitted