Counts of occurrence per depth in 青森県津軽南部 (Southern Tsugaru, Aomori Pref.) is shown as below graph,
Most of counts are occupied with 1km/10km/20km (total=97%). 1km, occupied 76%, had the longest silent term, and the last earthquake was in 2020. But, 10km/20km (the count is 2nd/3rd) are less than 1/5 of 1km. On addition to it, the greatest one of all depth is only M5.5 of 170km/200km. For the time being, no major change may be occurred unless huge outside earthquake were occurred.
note : Earthquakes with red font have the epicenters outside of this area.
- 1km (red)…The count is the 1st. There were 3times of major rapid increases before the longest silent term between 1985-2016. The 1st one was in 1972. The cause is unknown. The 2nd one was in 1978. 3 months ago, Off Miyagi Prefecture Earthquake (M7.4) had been occurred outside of this area. The 3rd one was occurred in 1983 as the aftershocks of the off the Paific Coast of Tohoku Earthquake (M7.7) . The largest one of 1km is only M3.8 in 1980.
- 10km(yellow)…The count is the 2nd. After the longest silent term between 1919-1973, the curve rose up following the 1st major rapid increase of 1km curve. But, the increase was fewer than 20km at that point. The largest one of 10km is M4.8 in 1986. After the M4.8, the curve slope became steeper, and overtook 20km in 2010.
- 20km(orange)…The count is the 3rd. After the 2nd longest silent term between 1986-1997, there was a rapid increase since 1997. But, then, 10km curve overtook 20km. The largest one of 20km is M4.6 in 1970.
- 30km(yellow green)…The count is only once, and the magnitude was unknown.
- 170km & 200km…The largest one of both 170km/200km is M5.5, and these M5.5 is the greatest ones of all depths.
- others…omitted.
