Wednesday, July 9, 2025

Counts of occurrence per depth in 青森県下北地方

Counts of occurrence per depth in 青森県下北地方 (Shimokita region, Aomori Pref.)is shown as below graph, 

1km&10km account for almost 85% of all depths. On the other hand,  the accounts of  40km-70km is nothing. The 3rd is 90km. The greatest one is M5.5 of 30km. It's the last one of 30km of only 3 times occurrence.


  • 1km (red)…The count is the 2nd. The count increased rapidly in Jan/1968. Most of them were magnitude unknown. As The Tokachi−oki Earthquake (M7.4) was occurred  in May/1968, they might be the foreshocks of the M7.4 even though the epicenter was outside of this area of the East offshore Aomori region. About 4 years later, the largest earthquake of 1km as M5.1 was occurred in 1972. Further after that, the longest silent term of 1km was occurred between 1982 and 2015.  
  • 10km(yellow)…The count is the 1st. There was the longest silent term between 1945 - 1958. After it, the silent terms became shorter. After the M4.9 of 90km in 1992, the 4th longest silent term was closed as between 1982-1993. about 3 years later, the slope of 10km curve has became steeper. Furthermore, the rapid increase has been occurred since May/2010. It seems one of the sign of Great East Japan Earthquake M9.0 in Mar/2011. The rapid increase has been kept still. The largest one of 10km is M4.7 in 1932. 
  • 20km(orange)…The count is the 6th as same 80km. The count is only 4 times. The largest one of 20km is M4.0 in 1976.  
  • 30km(yellow green)…The count is only 2 times. But, the last one was M5.5 in 1947, and the greatest one of all depths.
  • 40km-70km…no occurrence.
  • 80km(orange)…The count is the 6th as same 20km. The count is only 4 times. The largest one of 20km is M3.9 in 1967, and the last occurrence.
  • 90km(brown)…The count is the 3rd. The longest silent term is between 1958 - 1990.  The largest one of 20km is M4.9 in 1992.
  • 100km&110km…The counts are the 4th. But, only 5 times.
  • others … omitted.  
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    Counts of occurrence per depth in 青森県下北地方

    Counts of occurrence per depth in  青森県下北地方 (Shimokita region, Aomori Pref.)is shown as below graph,  1km&10km account for almost 85% of...