Check out the Red Cross disaster preparedness sites. They have this down. The key is water, food, and proper clothing/sleep kit. Your dehydrated food might keep reasonably well in a cool, dark place, but it will have to be vacuum sealed. And the stock must be rotated. Freeze dried food works better in this regard, as it has a great shelf life.
I keep a similiar kit ready at all times, even though we don't have many disasters here in Colorado. I have 6 one-gallon jugs of water, a week's worth of FD food, minimal kitchen setup, medical kit, flashlights/lithium batteries, canister stove and lantern and a bunch of 200 g canisters. I can choose from several sleeping bags and tents on the way out the door, as well as proper clothing for the season and altitude. My personal kit fits into a GoLite Pinnacle pack (not counting the water).
I suppose that I'm a gear-geek in many ways. This particular one relates to my Federal disaster medical response team activity. When we deploy (as for a hurricane), we need to carry gear and food to get us through at least the first 3 days at the disaster site. So that means MREs for self-contained meals (recommended, even though they get boring after a few days), and at least a day's worth of water (we can usually snag bottles of water when we get there). But don't forget to pack things like medicines, personal hygiene items, and also some version of entertainment (deck of cards, paperback books, etc.). Try to get into the habit of keeping your gas tank pretty full at all times, just in case you have to quickly bug out.
Just remember that in many disasters, including most earthquakes, you lose electricity. So don't pack any electrical devices, except perhaps your cell phone charger (in case you do have power). Speaking of cell phones, when disaster hits, the cell towers get innundated with local calls. It works best if you make your phone calls to another state, where you have a friend that can act as a clearing house and disseminate your information to others. You'll need to make sure that all of your local contacts, like immediate family members, know the out-of-state number to call. I know this sounds odd, but it somehow takes the pressure off the local cell matrix.
Unlike trying to pare your backpack down to the barest necessities, this exercise allows you to pack for certain insecurities. Providing there's enough room in your car to carry it all. I think of this like I do when car camping–have a succinct collection of gear and food/water that will allow you to get along OK for a few days. In this case, don't forget to take some disposable face masks. I'll bet there are hordes of Japanese living near the nuclear reactors that wish they had some.
Hope some of this helps…