Northridge was indeed "just" Magnitude 6.7
Keep in mind the energy release, and thus destructive power of a quake, goes up 1.4 times for each .1 magnitude, 3 times for each .3 magnitude, 5.5 times for each .5 magnitude, and 32 times for each full magnitude point.
Northridge was 32 times more powerful than this quake in Iran, for example.
The biggest credible quake you could get directly under LA is in the 7.2 to 7.4 range, or upwards of of 5+ times more powerful than Northridge.
That scares the heck outta me. Although my family came here from Germany in the 1870s and not one was hurt in any way by a quake.
Maybe I am in denial.