I live in the San Francisco Bay Area so the risk of a major quake that will disrupt power, water and roads is very real. I have 12 one gallon bottles of water in their boxes bought when they were on sale for a buck a piece. I store it in my basement next to the outside door so I can probably get to them even if the house has major structural issues.
Water is important. You can live for a week or more without food. But no water will do you in after a few days. In a major earthquake, it is very likely that the water system will fail. Broken pipes, lack of power, contaminated supply, etc.
Food is probably not a big issue. You probably have 4 or 5 days of food in your kitchen. Those cans in the back of the cupboard, soup mix, rice, beans or other dry goods. It may not be very appetizing, but it is food.
In America we are lucky. In the event of a major earthquake or other natural disaster, the rest of the country will rally. Food, water, tents, bedding will be brought in in a matter of days. You just have to plan for the first 96 hours.