Yeah, it made me go "hmmmm" also. The SCSN focal mechanism is: One of the 2 possible faults (nodal planes) has mostly vertical slip on a vertical fault, the other has oblique slip on a low-angle fault. Could be that they will post another solution later that will be different, although I suppose either solution could be correct.
There have been 4s closer to the southern San Andreas that have not triggered anything big over the last few years...
Chris

• focal mechanism