Freepers and their families get out before it goes.
Not sure, but I do know it’s a large amount of helium coming out of the ground that usually sends the animals running ahead of time.
Although in a big city there is not much natural life.
I don't live in California but I have to say, when talking about these sorts of geological inevitabilities it's hard to plan your life around them. For instance eventually the super volcano we call Yellowstone will go off and take most of the USA with it. It has happened before and it will again, in geological terms "soon". But that means maybe within something like 5,000 years. Could be tomorrow, could be year 4589. I can't wrap my arms around being so risk averse as to put in place a plan to avoid that. Because if you do, you have to consider all the other extremely remote possibility catastrophes that are always possible, everywhere and essentially just shut down.