Steve, I had missed this. The last couple of months the USGS global list page does not have a link to USA map that I can find. So, for California I go in via SCEC and not as often.

Yes, the swarm you note could be of concern. Is right near where the San Andreas fault proper crosses Salton Sea. It would be interesting to see whether all these quakes are "real"; whether they are still on map in a day. At coast there in SE is a geothermal energy plant. The depths range from 1 km to 8 km. I'm guessing, but if really a bunch of them are at 1 - 3 km depth, may be less likely to set off a big one (although they could be symptom of something going on deep).

keep us posted.

Chris