In addition to Roger finding no or nearly no relationships, John V., who has looked for this, also has posted in the past multiple times that there is no large effect. Maya Tolstoy and others found some relation in the spreading center between the Pacific and Juan de Fuca plates: there are magma chambers.

There have been so few M9 quakes in last 100 years that you probbaly can't tell anything. M8+ would be more significant if there is any relation or lack of relation.
Canie, if you make (a) graph, can you post it/them?

I'm one to talk: I should post graphics and do not.

Chris