Counts of occurrence per depth in 福島県中通り

 Counts of occurrence per depth in 福島県中通り（Nakadori area of Fukushima Pref.）is shown as below graph, 

1km-50km curves (except 40km) jumped up by M9.0 Great East Japan Earthquake far from this area. Most earthquakes were occurred in 10km (72%). Most of remaining were occurred both in the shallow depths(1km/20km) and in intermediate depths (70km-100km). Others are only 9% in this area.  The huge aftershocks in 2011 was occurred on the triple junction of 10km/20km/30km as M5.5 of 10km. The aftershocks continued increasing further, and led to M7.0 of 10km one month later. The M7.0 of 10km is the greatest magnitude of all depths in this area. On the next day, M6.4 was also occurred on the quintet junction among 10km-50km. Before the M9.0, the longest silent terms of 1km-20km had been continued. They were interrupt by the aftershocks. They seem to be the sign of the M9.0.

1km (red)…The count is the 2nd. There was the rapid increase by M5.7 of 1km in 1924. The rapid increase made the rank of the 1st keep for long time until 2010. The silent terms became longer gradually after the rapid increase. The longest silent term was occurred between 1976-2011.  M9.0 Great East Japan Earthquake was occurred, and the aftershocks broke down the longest silent term. The M9.0 induced both M7.0 of 10km and the many aftershocks of 1km-50km except 40km. The M7.0 is the largest magnitude of 1km. Because of less aftershocks of 1km than 10km, the rank went down to the 2nd. 

10km (yellow)…The count is the 1st. Before the M9.0, the curve was located under 100km curve since 1960. The longest silent term is between 1971-2011. The interruption was occurred by the aftershocks of the M9.0 as same as 1km. The huge aftershocks in 2011 was occurred on the triple junction of 10km/20km/30km as M5.5 of 10km, and the count rank became the 1st. After the M5.5, the max magnitude was bigger and bigger via other depth junctions. Finally, M7.0 of 10km was occurred 1 month later. The M7.0 is the greatest one of all depths. 

20km(orange)…The count is the 3rd. As same as 10km, the curve was located under 100km curve since 1960. The longest silent term is between 1956-2011. The interruption was occurred by the aftershocks of the M9.0 in 2011 as same as 1km/10km. These longest silent terms of 1km/10km/20km seem to be the sign of M9.0. The rapid increase made the rank go up to the 3rd. M6.4 was also occurred on the quintet junction among 10km-50km. The largest magnitude of 20km is M6.5 in 1922.

90km(brown)…The count is the 4th. The 90km curve has been increased almost constantly. The curve was overtaken by 10km/20km aftershocks of the M9.0. But, 90km curve is closing to 20km recently. The largest magnitude of 90km is M5.4 in 1985.  

80km(navy)…The count is the 5th. 80km curve was going up and down 90km curve. The largest magnitude of 90km is M5.3 in 1924.  

70km(purple)…The count is the 6th. 70km curve was going up and down 90km/80km curves. The largest magnitude of 90km is M5.7 in 1957.   

others… Remaining counts except above depths are only 9%.