[Island Chris]

The swarm has at east three M4+ quakes. Those are all strike-slip. There are shallow: just a few km. They are aligned NE-SE and there precision on horizontal location is only 0.2 km. Thus, the zone that is moving a little bit is left-lateral. There are known cross faults, striking at a high angle to the San Andreas fault, in this area. One of these failed in a M6.2 left-lateral earthquake in 1987 (Ellmore Ranch), and that quake triggered the larger (M6.7?) Superstition Hills right-lateral quake within less than a day. I am doing this from memory; not checking online; if you are interested and the detail matters, you may want to check my previous sentence
Chris