Analysis for the Area chart of epicenter(Magnitude)-2

The 5th "Accumulated value Chart" is for The Iwate-Miyagi Nairiku Earthquake (M7.2) in 2008 as below,

There were 2 major peak. One was M7.1 in 2003. The other was M7.2 in 2008.They changed the pattern of the depth distribution in this area before and after completely. Great East Japan Earthquake changed in 2011 also, but, no remarkable peak there was. The difference between 3 earthquakes are listed in the table.

To clear the effect of the red area(1km), only 1km accumulated is picked up as below,

As the horizontal axis is non-linear, they have the different scale between full depth and only 1km. Before M7.2 in Jun 2008, there was small red area peak in Des 2007. It seems to be the advanced sign of M7.2.No peak was caused by no data of magnitude of "Details unknown". They are treated as 1 km depth class of epicenter in my site.(It's never the official opinion of Japan Meteorological Agency.)