It's not unusual for phantom quakes to turn up on USGS' real-time web page when there's a big one in the area (and sometimes even across the world). Most are cleaned up within an hour or so. That said, the Geysers area is always jiggling anyway, so a few microquakes triggered by something the size of this afternoon's south of Mexicali wouldn't be unusual. A little line extending west just N of the border in the most recent plot is interesting. It sure lit up the SoCal seismo monitors!

Probably slowing or stopping a lot of trains too. SP runs through that area on the way to Yuma (though so far nothing bigger than "micro" or "minor" seems to be popping up on that side of the Valley), and it was probably strong enough to briefly trip some systems in LA and SD especially transit.