Counts of occurrence per depth in 釧路沖

 Counts of occurrence per depth in 釧路沖 (Kushiro offshore region) is shown as below graph, 

Though 1km is the 1st count curve, after the longest silent term, no occurrence. M8.2 of 50km occurred around the quintet junction of 50km / 40km / 20km / 60km / 10km in 1952. M8.2 of 50km kept most of potential until M8.0 of 50km in 2003. On the other hand, M7.5 of 100km was caused by the quartet junction of 10km/70km/80km/100km in 1993. 50km curve has the steep slope. So, 50km may catch up with 1km in future. It may cause of the domino reaction with other(s). 

• 1km(red)…This count is the 1st. But, the longest silent term is continuing since 1994 after the 2nd longest one between 1980-1994. The rapid increase was just after M8.2 of 50km in 1952. The M8.2 of 50km is the greatest magnitude of all depths. The largest magnitude of 1km is M6.9 in 1935. 
• 50km(light blue)…This count is the 2nd. As described above, The greatest magnitude of 50km is M8.2 in 1952. The M8.2 was occurred around the quintet junction of the curves among 50km/40km/20km/60km/10km. After the M8.2, the count was accelerated by M7.2, and caught and overtook 40km around 1968. Since it, 50km/40km curves almost overlapped each other. M8.0 of 50km in 2003 seems to be the result of the combined earthquakes of 50km/40km kept the most energy of M8.2 in 1952. The curve is keeping the large slope. So, 50km may catch with 1km in future.
• 40km(green)…This count is the 3rd. The greatest magnitude is M7.4 in 1973. The M7.4 caused not only the combined rapid increases of 40km/50km, but also 30km/20km's ones as the aftershocks. The overlapped of 40km/50km almost continued until M8.0 of 50km in 2003. After it, 50km was accelerated by M7.1 of 50km in 2004. So, 40km curve lagged behind from 50km. 
• 60km(blue)…This count is the 4th. The curve shows the similar pattern with 50km with low level. In recent years, it almost overlapped with 30km. There were 2 major rapid increases by M7.4 of 40km in 1973/M8.0 of 50km in 2003. The largest magnitude is M7.1 in 2008. 
• 30km(yellow green)…This count is the 5th.The curve followed 60km. But, after M8.0 of 50km in 2003, the increase becomes slow down. The pattern of 30km/50km after the M8.0 resembles with the one of 40km/50km. The largest magnitude is M7.1 in 2008 after the slow down. 
• 20km(orange)…This count is the 6th. There was the entanglement among 10km/20km/30km/60km after M7.2 of 50km in 1961, and separated from each other after M7.4 of 40km in 1973. Later, 20km/10km had the longer silent terms including the longest silent term. Recently, the curve slopes of them have become steep a little bit. It might be the sign of more activity of them than before. The largest magnitude is M6.2 in 1921.
• 70km(purple)…This count is the 6th. 70km/80km curves were overtaking and being overtaken each other. 100km curve joined the entanglement of them after M7.5 of 100km in 1993 until about M7.1 of 30km in 2008. 70km curve become more steep, and caught up with 20km around in 2000. The largest magnitude is M6.3 in 1927.  
• 80km(navy)/100km(gray)…The count is the 7th/8th. After the  entanglement among 70km/80km/100km after M7.5 of 100km in 1993, 80km / 100km curves are still overlapped each other. The largest magnitude is M6.5 in 1949(80km)/M7.5 in 1993 (100km).  
• 90km(brown)…This count is the 9th. The the largest magnitude is M6.3 in 1953.  
• 10km(yellow)…This count is the 10th. The the largest magnitude is M7.1 in 2008. Because of these values, the potential seems to be high even the low ranking.
• others…omitted.