According to the news here in LA tonight the study focused on the San Andreas Fault, Elsinore and San Jacinto faults. Study took into account GPS data, combined with status of known faults and a look at past faults that have had historical ruptures to get this info.

What I want to add to this is, the way its being issued is kinda abstract. As you just mentioned, we've had a lot of those quakes already. In my VERY amateur research, I've seen in last 130 years there has been at least a 6 quake SOMEWHERE in s. cal every decade. In addition I've observed the central coast of CA gets a 6+ every 25 years on clockwork.

So I guess what I'm saying is they should have been more forthcoming and said buzz words, "LOS ANGELES" or "SAN FRANCISCO" because we could have a 6.8 in the remote desert tomorrow, LA will sway mildly for a minute then average citizen will say, "whew that was the one in news, don't have to be prepared now" ...when there could be the 7 lurking Palos Verdes all the way up to Ventura.