Glen...from your link and the location, looks like the quake is near the stepover between Imperial fault and Cerro Prieto fault....Cerro Prieto spreading center is located near there (I did not locate this carefully...just by eye on the figure you link to). The topography on the map on your link and the topography on the USGS map also indicate this. I suppose Cerro Prieto volcano must be near there. Someone may want to plot this carefully...googleearth might be cool...Don?
Chris