Counts of occurrence per depth in 十勝地方中部

Counts of occurrence per depth in 十勝地方中部 (Middle Tokachi region) is shown as below graph, 

note : There are not included of all depths to avoid too complicated curves. 

• 1km (red)…This count of the earthquakes is the 1st one. There was a rapid increase of the count after M6.2 in 1921. But, the the increase has stopped in 1972. The max magnitude is only M4.9 in 1934.
• 100km(gray)…This count is the 2th. Around 100km in deep, the counts are larger than others of shallow deeps.The max magnitude is M6.5 in 2013. This value is the max of all depths also.         
  
• 90km(brown)…This count is the 3rd as same as 120km. After M6.5 of 100km in 2013, there was a long silent term between 2014-2021. In result, the count hasn't increased so far though the curve seems to follow 100km. The max magnitude is M5.1 in 1953.
• 80km(navy blue)…This count is the 4th following 90km. But, the the increase has stopped in 2022. The max magnitude is M5.9 in 1942. Because of the high value of the max magnitude, the count may become more later.
• 110km(blue) …This count is the 6th. The max magnitude is M5.2 in 1997, and the count curve rises up rapidly in recent. The curve may catch up with 100km.
• 10km(yellow) …This count is the 10th. There was the longest silent term between 1972-2003(21 years).  After it, the count increases little bit, and the count is staying low still.
• 20km-50km…These counts are the 11th-13th. Unless there is some big earthquake, the ranks should stay lower than ones of around 100km. 40km's max magnitude is M6.0. So, the count may become easier than others of 20-50km.