Susan,

Do you drive the same Suburban every time?

Could you break a few things out into pouches that you could put on your backpack's hip belt and shoulder belts?

Perhaps the pouches could be stuffed under the seats. I'm thinking a pouch that has some energy bars. Another that has essentials such as are in Doug's PSK.

Sounds like you often have passengers - would that be good or bad when an earthquake strikes? That many more peops in the vehicle needing water and food....

But I'd rather not be alone. Depends on the peops, I guess.