The automatic locations and hypocenters for a M3.9 and M3.1 aftershock both show strike-slip, and both are very shallow (less than 2 km) with small errors. We'll have to look at whether the depth changes. From the map, it looks like the quakes are south of the N-dipping Cucamonga fault, which is thrust with probably some left-lateral mixed in somewhere.
The earthquake may turn out to be on the NW-SE right-lateral nodal plane (as a guess). I have my computer running Gocad loaded with the SCEC Community fault model at home this weekend...maybe if I have time later I'll convert the lat-long-depth to UTM zone 11 X Y depth, and see if the Community Fault models shows any faults within the errors of this quake.
Wait...the license expired Feb 29...guess I can't do that (we will be getting new license).
Chris