May as well start off where everyone else does.
Buy a few guns, learn to filter your own water, and be cool with eating roots, bugs, and maybe some human flesh every once in a while and you're gonna be fine. The Bay Area is going to be a cornucopia of easy pickings.
Seriously, though, read this book, build the recommended kits (they're very small and extremely portable), and spend a weekend practicing the recommended skills like building fire and shelter in the National Parks/Forests: https://www.amazon.com/gp/product/B00M719VG4/ref=dbs_a_def_rwt_hsch_vapi_taft_p1_i0
You can shortcut a lot of it buy buying the small items on Amazon (torch lighter, Life Straw, etc.).
Keep the tiny kit on your person at all times, the other in your car or in a safe location nobody knows about.
Once disaster hits, you're going to want to get out of the city as fast as possible.
The Bay Area is in no way shape or form ready to absorb the damage from a catastrophic earthquake. Our highways and infrastructure already grind to a halt during rush hour.
And remember when the vineyards were on fire and the human garbage came from all around to loot the abandoned homes? Those are the types of people you have to worry about, because they'll be attracted to the carnage like flies to shit.
A Guide to Canning, Freezing, Curing & Smoking Meat, Fish & Game
These are the minimum I would want.