The only “catastrophic” seismic event that could conceivably happen to California (besides run of the mill things breaking) would be the uplift or pinching shut of the golden gate and subsequent damming of the Sacramento/San Joaquin river complexes resulting in the flooding of the delta and valley. I would hope that the people running the show here would breach that well before it became a problem.
It’s not going to sink, or break off and float away...
We can all dream...