How do tsunami early warning systems detect deadly waves in time?

The answer

The Pacific Tsunami Warning Center, established in 1949, coordinates a global network of 71 DART (Deep-ocean Assessment and Reporting of Tsunamis) buoys. Each DART station consists of a bottom pressure recorder anchored at depths up to 6,000 meters, connected to a surface buoy that relays data via satellite. These sensors detect tsunami waves as small as one centimeter in open ocean, where tsunamis travel at 800 kilometers per hour but are barely perceptible at the surface. After the devastating 2004 Indian Ocean tsunami that killed over 230,000 people, the Indian Ocean Tsunami Warning System was established in 2006. Modern systems combine seismic detection, DART buoys, coastal tide gauges, and GNSS sensors to issue warnings within minutes of an earthquake.