Don

A number of people have been checking whether regions are more susceptible to earthquake triggering just before a large earthquake, and it doesn't seem to hold true. There is some indication earthquake-tide correlations pick up just prior to a large event (Tanaka, 2002, GRL), but other find the contrary (Sammis and Smith). One careful test showed LESS triggering by dynamic waves in an area that soon afterward had a large quake.

A new idea in southern California is that entire networks of faults can break over a few centuries, then be quiet for a millenium or two (Rockwell, Dolan).

The timescales and distance scales of triggering are not yet clear, and triggering is sufficiently weak and uncertain that it hasn't affected estimates of risk, except for higher risk from close-in aftershocks.

John