Counts of occurrence per depth in 宮城県南部

Counts of occurrence per depth in 宮城県南部（Southern Miyagi Pref.） is shown as below graph, 

1km/10km are 2 tops of count ranking. Next is 90km. 20km-80km are low ranks under 6th including no occurrences. Most of 1km were unknown details (with no magnitude data). 

• 1km (red)…The count is the 1st. Most of them (1767times) were unknown details (with no magnitude data) except only 5 times. The rapid increase was occurred in 1938. They may be caused by aftershocks of M7.1 of 60km in 1937 (The epicenter was off the coast of Miyagi Prefecture outside of this area). After the rapid increase, the silent terms became longer and longer. The longest silent term is between 1975-2005. The next longest silent term is continuing still now (for 20 years).  The largest earthquake of 1km is M4.4 in 1962.   
• 10km(yellow)…The count is the 2nd.  After the long silent terms including 2nd / 3rd, M6.0 of 10km was occurred in 1956. The M6.0 is the greatest one of all depths. There were 2 major rapid increases both in 1998/2011. Both of then were caused by M5.2s of 10km. In result, the count has approached very nearby 1km's one.
• 90km(brown)…The count is the 3rd. During 1950-1990, 90km curve were back and forth of 10km curve. But, during the longest silent term of 90km between 1986-1999, the curve became far from 10km curve. The largest earthquake of 90km is M5.9 in 1960. The M5.9 was occurred at the timing of overtaking 100km curve.
• 100km(gray)…The count is the 4th. After being overtaken by 90km in 1960, the silent terms became longer. The largest earthquake of 100km is M5.0 in 1947. 
• 110km(gray)…The count is the 5th. The largest earthquake of 110km is M5.0 in 1951.  
• 20km(orange)…The count is the 6th as same as 120km. There was the longest silent term between 1936-1999 for 63 years. The largest earthquake of 20km is M4.0 in 2011. 
• others…omitted.