If you are an American citizen caught up in a natural disaster or civil disturbance, you should inform your relatives as soon as possible that you are safe, or contact the U.S. Consulate who will pass that message to your family through the Department of State. Be resourceful. U.S. officials will do everything they can to contact and advise you. However, they must give priority to Americans who have been hurt or are in immediate danger. In a disaster, employees of the consulate face the same constraints you do – lack of electricity, fuel, interrupted phone lines, closed airports, etc.
For more information please go to travel.state.gov – Natural Disasters.