DTT, have you called your local propane provider? I know around here you can get a large tank for a delivery fee and having it filled up. It will cost more for installation but you can also have the tanks buried, not completely buried, just the top of the tank would be seen. All of this is speculation on my part because i live in the land of sink holes and hurricanes not earthquakes.

I would recommend checking the fuel consumption of your generator choice before getting the tanks. From your post i am assuming if you are getting a automatic transfer switch that you are not getting a small generator. Whole house generators can easily drink a couple of gallons an hour or more i was talking to my propane delivery guy after several hurricanes passed though here and he said that a number of his customers have big propane generators that went though $600 to $800 in propane in a week. That's several hundred gallons of propane in a week. IIRC a 40# bottle is less than 10 gallons of propane, so you will be changing tanks every 5 hours. A large tank would at least allow you to run for a couple of days before needing a refill. And your propane provider will be happy to come out and refill it every couple of days if there is a long term outage.