Well from a very amateur point of view (meaning I have no numbers/stats to back me up) I can tell you that indeed CA does SEEM to go through on and off periods.

other times I can remember were in June of 2005, 2 5s in the desert then a 7+ off the coast of Mendocino.

In 1992 we saw Joshua Tree then within a week a pair of 6+ quakes near Eureka.

In October of 2001 all of Southern CA definetly saw a heightened level of activity.

Indeed in past the state has lit up so to speak. Scientists say its coincidence. But is it? I mean we go through LONG periods of quiet, I always suspect its all somehow related.