There was a M4.5 thrust (slightly oblique) quake...I think towards the west end of Northridge rupture (am not checking closely so don't know if it is on the S-dipping or N-dipping fault system). The area west of Northridge is at very high risk: horrible basin conditions (very deep narrow Ventura basin, probably the most active thrust faults in southern California, and either no earthquake on them in historic time or since 1812, depending on whether the big quake seen in Trench on San Cayatano fault was 1812 or earlier (it postdates 16 something....Dolan, Rockwell, others (BSSA??).
I'm an expert on these fault systems, but west of where this quake occurred.
Chris