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

For the prediction of magnitude earthquake, envelope lines seem to be useful.

The  line chart of magnitude in Sanriku-oki Area (rectangle area) with envelope lines is as below,

There are 2 kind of envelope lines. One is the top envelope lines for local maximum plots. The other is the bottom envelope lines for local minimum plots. For local period, all magnitude values with it are between top/bottom lines. Crossing these envelope lines may shows the pattern changes, and the too more/less excess values may often be the sign of sudden change like rapid increase of later value. As showed the previous page, sometimes the top envelope line of short term covers the excess value from the envelope line of long term. Around in 2007, there were rapid divergence of magnitude range between top/bottom envelope lines just after rapid convergence of them. It seems some sign of M9.0.