I've been looking at that.

There's no significant or named faults in the specific area of the quakes, but given the geography, there's almost certainly unknown ones. (my opinion)

I've got a USGS geological map as a PDF. I'll see if I can import the image and georeference it to Google maps as an overlay to generate some visuals.

I have a hunch this may be on the far north end of the San Cristianitos fault which ends a few miles south of the quakes location. If you imagine an extension (not unreasonable given the geomorphology) these quakes are on that. (I need to check the beach balls)

The San Cristianitos fault is famous as being the one that the San Onofre nuclear power generating station practically sits on.

I hike these mountains, and I have seen fault traces, one of which I think is the San Cristianitos fault, quite accessible, and with some fossils nearby.

Brian