The resulting shockwave caused massive waves that killed an estimated 160,000 people in Indonesia, Thailand, India, Sri Lanka, the Maldives, and other locations in the Indian Ocean basin, making it the most lethal tsunami in recorded history. On 26 December 2004 a megathrust earthquake (9.0 Richter scale) occurred along the India-Burma plates was such an event, in which an estimated 750 miles (1,200 km) of fault line slipped 60 feet (20 m) and vertically raised the Burma plate a few meters. Not all earthquakes generate tsunamis, since it usually takes an earthquake with a Richter magnitude exceeding 7.5 to produce a destructive tsunami. These usually occur in regions of the earth along active tectonic plate boundaries, particularly along the Pacific Ocean's “Ring of Fire” – a circle of active tectonic plate boundaries stretching from Indonesia to Japan, to the Aleutian Islands, to the west coast of North America and south all the way to Chile – but also in the Atlantic and Indian Oceans as well. Thus, the Japanese word tsunami or “harbor wave” is a more inclusive term and has been internationally adopted because it covers all forms of impulse wave generation.īy far, the most destructive tsunamis are generated from large, shallow earthquakes with an epicenter or fault line near or on the ocean floor. But tsunami waves are not the same as astronomical tide waves, nor are they caused by the normal gravitational influences of the moon, sun, and the planets.
The term "tidal wave" was often erroneously used to describe the same phenomenon, particularly because of the sudden tide-like retreat of water from the coast as the tsunami wave closed the shore. The word tsunami is composed of the Japanese words "tsu" (which means harbor) and "nami" (which means wave).
In contrast to These waves can reach 90 feet (30 m) in height and the larger tsunamis have caused great destruction and loss of life across entire ocean basins. Naval Humanitarian Operations by Adam Siegel Navy Relief Efforts after the Indian Ocean Tsunami, 26 December 2004Ī Sampling of U.S. Vessels Lost and Salvaged, Report of the Secretary of the Navy, 1916 Reports of USS Powhatan and USS Wateree, 1868 Injury and Destruction of Vessels by Earthquakes, Report of the Secretary of the Navy, December 1868
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