The focal mechanism of the M5 is strike-slip. I don't know the area, but there are apparently active right-lateral faults that cut that part of California....some have not been mapped or even discovered yet. Caitlin Lippincott, a distance cousin, showed one her group found at the coast in northern California somewhere...maybe at the 2006 SSA meeting or a SCEC meeting. According to her(?) the inland parts of California there are pretty rugged/vegetated. (?)

There was a M4.0 also late yesterday offshore south-central California. By coincidence, we were looking at a fault that offsets Arguello canyon...a couple tens of km southeast of the quake. The quake could be on the same fault or a related fault.

Chris