Early Warning Systems Around the World

The absence of a functioning ocean-wide early warning system was starkly exposed by the Indian Ocean earthquake and tsunami of December 26, 2004, a magnitude 9.1 undersea rupture off the coast of Sumatra that produced waves killing roughly 230,000 people across fourteen countries, most without any warning of the wave's approach for the one to seven hours it took to reach different coastlines. In direct response, UNESCO's Intergovernmental Oceanographic Commission coordinated the establishment of the Indian Ocean Tsunami Warning and Mitigation System (IOTWMS), which became operational in 2006 and now links seismic monitoring stations, deep-ocean pressure sensors, and coastal sea-level gauges across the region to national tsunami warning centers in countries including Indonesia, India, and Australia.