2 cents
Stats on the ring maps were produced on a number of occasions for this board in the
past. They have consistently shown between a 50 and 300% increase in activity
in designated rings over background following large earthquake. If you search through
the archives you will find these statistics. These statistics have been based on
several hundred cases, so lack of associated data is not a problem.
By the way, a statistical map of the type you folks have been discussing has been
produced, but not made available to this forum. I cannot discuss the precise details
of what is done, but it shows strong evidence that the large earthquakes are associated
with increased activity at the noted rings and also does often show the location of
strong subsequent quakes. Because of restrictions on discussing this, that is about all
I can say, however. The statistics and the map demonstrate that this is probably
not an illusion, and the physics of how it can happen is quite simple to understand.