And another M4...east of Bakersfield. Both are strike-slip. Things are acting up. It really seems like there are periods where California is turned on and those when it is turned off. I don't think Roger would confirm that with statistics though. It has been well-known that this can happen...there were 2 large quakes the same day on 1986: offshore Oceanside (M5.5?) and Long Valley/Mammoth (M6?)...they may be too far apart for static stress to trigger at that magnitude. I'm doing this from memory and may be wrong.
Chris