Cathryn, There was an appoximately M5.0 (maybe 4.9?) in 1979, and another of about the same size in 1989. There was something perhaps a little bigger in 1930. The 1979 and 1989 quakes and aftershocks were located offshore near the west plunge of the same fold that makes Palos Verdes Hills. The main shocks were thrust/reverse. K.B., others, me have interpreted a big NE dipping fault to project in to the Compton thrust ramp beneath LA. Our faults can explain the fold, but project above most of the quakes, including the big ones.

The 1930 quake was relocated by Hausson to near the offshore Santa Monica fault.

In 1989 after the quake, Johnie Carson put in about 20 rapid fire quake jokes in his monologue. I saw this then, but would love to get ahold of it now.

Also, there have been several near M3 quakes in the last couple of months in the Playa del Rey onshore, offshore from there, and most recently, as posted, in San Pedro Basin...

The faults out there are big enough to have much larger quakes than M5s. There are blind thrust faults and there are strike-slip faults.
Chris