My understanding is that, at least for the SCEC maps, those are preliminary automatic solutions - not reviewed. Once reviewed, they may move or disappear altogether. I've seen that happen on occasion.

This has given me the idea of looking for temporal patterns in the quakes. I think there is enough completeness to the catalogs going back far enough that maybe something would show, at least for SoCal if not Ca/Nv as a whole.

The trick, though, would be to look at specific region groups. Not arbitrarily defined by lat/lon boundaries, but defined based on the fault structures.

Brian