The trouble is, we're always under prepared for a mega disaster because we don't know which direction the disaster is coming from.
"I shall move to the Tetons to await the coming nuclear apocalypse!"
And then the volcano under Yellowstone blows.
Yeah, I don't see how you prepare for a mega disaster. But I always keep a few things on hand for a mini disaster -- a few gallons of water, batteries, flashlights, a little radio, some canned stuff, a manual can opener, etc. That habit has stood me in good stead through blackouts and such.
I also have kept my land line and an "old-fashioned" phone with a curly cord attaching the receiver to the base. If there's a blackout or disaster, cell phones can run out of juice, and your cordless phone won't work without electricity (some folks don't know that!). But odds are, your old-fashioned phone attached to an old-fashioned land line will continue to work. Laugh all you like -- during the last blackout in NYC, a lot of people wanted to use my phone!
If there's a mega disaster, the cyanide and gun might be the best bet.