The 2004 Sumatra-Andaman Earthquake and Tsunami in the Indian Ocean

The December 26, 2004, Sumatra earthquake (Mw 9.1) generated tsunamis that propagated across the Indian Ocean and caused the worst tsunami disaster. Factors contributed to the tragedy include the giant size of the earthquake, absence of both tsunami warning system and long-term forecast of future earthquakes in the Indian Ocean. Significant seismological development since 1960, when the Chilean earthquake (Mw 9.5) caused Pacific-wide tsunami damage, makes it possible to estimate the source parameters within minutes after large earthquakes and utilize it for the tsunami warning purposes. Tsunami propagation in deep ocean is rather simple; the velocity depends only on water depth, hence the propagation and coastal behavior can be modeled by numerical simulation. Computer simulation of the 2004 Indian Ocean tsunami reproduced the observed features. In order to understand what happened in the past and what will happen in the future, geological and historical studies of past earthquakes are important. Paleoseismological studies in Pacific Rim revealed that earthquakes similar to the 2004 event occurred in the past. Several tsunami warning centers monitor earthquakes around the world and send tsunami warnings to circum-Pacific countries. For tsunami hazard reduction, infrastructure to disseminate warning information, assessment of tsunami hazard, and education are also important.