The first thing you must have in an earthquake kit is a pistol.
Those who are not prepared will resort to force to get resources out of those who have them.
So you want a pistol.
Most of the other items are obvious: food, water, flashlight, radio, cash, batteries.
And the other nice thing about the pistol is if you run out of anything, well, just grab the pistol and go find someone who has a robust earthquake kit sans pistol.