This area is also a huge contender for a quake in the 6-7 range. Its loaded with blind thrust faults that are being squeezed tighter as the San Andreas to the east continues its march to the north. I read a paper once that this whole chunk of Socal has the potential to give off 6+ quakes every few years or so-Northridge and Sylmar (71) are considered part of the southern border of the system. Obviously there have been no regular quakes of 6+ in recent times but in the 1920s there were a few shakers out that way and evidence of historic large quakes out that area.