Folks in earthquake zones in the US are expected to have 72 hours of survival supplies on hand. There's a neat interactive publication I ran across the other day:
72 Hours Survival Plan
It works for pandemics, floods, terrorist attacks, and other disasters, as well. Some of the topics I hadn't thought of were pet supplies, back-up medications, cash, and bug-out bags (if you have to leave your home fast).
This was recently created for San Francisco residents by the government who told them they shouldn't expect to get help from the goverment before 72 hours. I imagine the situation is similar in Mexico.