My husband has a non-Californian fear of earth quakes. (I was born here – I take them as part of the landscape.)
He’s also an architect – so he went through and made the house itself more earth quake resistant…. It’s a 1960’s 2 story tract home. He added more bolts between the sill and foundation. He added a LOT more diagonal bracing… whenever he opens a wall for any reason, he reinforces it. He has taken the corners and replaced the drywall with plywood to add stiffening/sheer wall strength.
As far as generic preparedness – we always have an extra case of bottled water. (the one we’re using – and a full spare case.) We have the hand crank flashlights, we have data backed up and ready to grab. We have a lot of camping gear… The idea is that if we have to get out – for fire, earthquake, societal collapse – we’ve got the basics.
And I shop at Costco… so we always have bulk food. LOL.