Canie-you mean Gulf of California, not Mexico. The 4.3 looked to be a bit inland in Sonora. The little quakes near Simi Valley are of interest also: that may be near the west end of the Northridge rupture and there would be a stress concentration at the end of a rupture. The Oak Ridge fault would not be too far away. But, like the 2.8 in Parkfield, these little pops are not too unusual and may mean nothing....Chris