an OBS
Posted by John Vidale on August 04, 2009 at 10:59:14:

the offshore station is an OBS, cabled to land, I'd guess.

I'm not sure whether the map has all the events reported by the Bay-Area-based network in Northern California, probably not.

Follow Ups:
     ● OBS = Offshore Buoy Seismometer?  - Mike Williams in Arroyo Grande  21:01:29 - 8/4/2009  (75680)  (1)
        ● OBS = ocean bottom seismometer - John Vidale  23:03:33 - 8/4/2009  (75682)  (0)