Counts of occurrence per depth in 根室半島南東沖 (Southeast offshore the Nemuro Peninsula) is shown as below graph,
Though 1km is the 1st count curve, after the longest silent term, no occurrence. M7.4 of 40km occurred around the triple junction of 50km/40km/30km in 1973. After M7.4, these depths are keeping ranks between 2nd and 4th. On the other hand, shallow depths of 30km/20km/10km keeps lower ranks. Especially, even though 30km recorded M8.2 as the greatest one of all depths, 30km keeps the low rank. Such reversal status seems to be unstable with high stoked energy.
- 1km(red)…This count is the 1st. The increase continued steady until 1982. After it, the silent term became longer and longer. The longest one is between 1994-2016, and there is no new earthquake after the last one still now. The the largest magnitude is M6.9 twice in 1925/in 1935.
- 50km(light blue)…This count is the 2nd. The greatest magnitude of 50km is M7.1 in 1973. The M7.1 was occurred as the one of the aftershocks of M7.4 one week ago. There were 2 times of the major rapid increases when M7.4 of 40km in 1973/M8.2 of 30km in 1994. The count of 50km is still increasing now, and approaching to 1km.
- 40km(green)…This count is the 3rd. The greatest magnitude is M7.4 in 1973. The M7.4 was occurred round the triple junction of 50km / 40km / 30km. After the rapid increase by the aftershocks, the curve got tangled with 50km. But, after M7.0 of 60km in 2000, 40km's increase becomes slow down.
- 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/M8.2 of 30km in 1994. The the largest magnitude is M7.0 in 2000.
- 30km(yellow green)…This count is the 5th.The curve followed 40km. But, after M7.4 of 40km in 1973, the increase becomes slow down around the the triple junction of 50km / 40km / 30km. After the long silent term between 1984 - 1988, the silent term becomes shorter again. Then, M8.2 was occurred in 1994. The M8.2 is the greatest one of all depths. After the M8.2, the silent term becomes longer now. So, 60km overtakes 30km now.
- 70km(purple)…This count is the 6th. 70km overtook 20km around in 2015. The the largest magnitude is M6.3 in 1931.
- 20km(orange)…This count is the 7th. Though the curve almost overlapped with 60km before M8.2 of 30km in 1994, 20km became slow down against 60km rapid increase. The the largest magnitude is M6.2 in 1921.
- 80km(navy)…This count is the 8th. The the largest magnitude is M6.5 in 1949.
- 90km(brown)…This count is the 9th. The the largest magnitude is M6.2 in 1967.
- others…omitted
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