I've been lurking on DUTCHSINSE'S site for a couple of years, primarily because my daughter lived in earthquake-prone Oregon.
It appears deep quakes in New Zealand is the origin of earthquake progression. It is a mystery when and how large they will be.
For example, there's a theorem in topology that says that if you have a sphere covered with hair, it's impossible to comb it without at least one cowlick. Perhaps there's a similar result that if you have a molten globe covered with moving plates, there must be at least one location where energy "bubbles up" to force earthquakes. Perhaps if there are multiple such locations, they eventually converge into one.