Despite a lag of up to several hours between the earthquake and the impact of the tsunami, nearly all of the victims were taken completely by surprise. There were no tsunami warning systems in the Indian Ocean to detect tsunamis or to warn the general populace living around the ocean. Tsunami detection is not easy because while a tsunami is in deep water it has little height and a network of sensors is needed to detect it. Setting up the communications infrastructure to issue timely warnings is an even bigger problem, particularly in a relatively poor part of the world. A tsunami warning system is a system to detect tsunamis and issue warnings to prevent loss of life and property. It consists of two equally important components: a network of sensors to detect tsunamis and a communications infrastructure to issue timely alarms to permit evacuation of coastal areas.

CWarn
CWarn.org is a global tsunami warning and alert system.
CWarn monitors global earthquake activity and alerts its members, via an SMS text message on their mobile phones, should a tsunami threat be forecast for their particular location.
The CWarn system makes use of its member’s latitude and longitude, taken from the member’s address to calculate distance from the earthquake and possible threat levels.
All possibly effected members are sent an SMS message detailing earthquake magnitude, time, date, location and threat level. The system also allows for members to enter their travel itinerary before departure and their holiday whereabouts are remembered and computed accordingly.