Where did that image originate. Just curious.
2012 movie
BTW, there is no tectonic scenario where any significant portion of California “falls into the sea”.
The worst, or most interesting possibility depending on where you are, (I’m a geologist) would be if either the Central Valley shook long and hard enough to cause a significant sediment consolidation in areas and they back filled with sea water until equilibrium was reestablished OR activity raised the area of the golden gate enough that it restricted the outflow of water.
Another item of awesome coolness would be if a volcano was going to form there like Paricutin.