Just before 8 a.m. local time on December 26, 2004, the idyllic calm of a peaceful morning in Southeast Asia was shattered by one of the strongest earthquakes ever recorded. The epicenter was about 100 miles off the west coast of Sumatra. The magnitude of the earthquake was somewhere between MW9.1 and MW 9.3 on the Moment Magnitude Scale. This makes the Sumatra-Andaman Earthquake the third largest since seismographs have been in use, surpassed only by the Great Chilean Earthquake of 1960 (9.5) and the Alaskan Earthquake of 1964 9.2)
The quake was created in the subduction zone where the India Tectonic Plate is diving underneath the Burma Plate. The drifting of the plates caused a huge rupture underneath the sea floor of the Indian Ocean. This rupture, over 750 miles long, and 19 miles under the ocean bed caused the sea floor to rise violently, and created a vertical rise in the water level. As this huge displaced volume of water spread out, it caused a massive tsunami that inundated the coastlines of Indonesia, Sri Lanka, India, Thailand, Myanmar, the Maldvies and all the way over to Madagascar and eastern Africa. When the tsunami reached the coastlines of these countries it rose up into waves as high as 100 feet tall.
The tsunami consisted of a series of waves arriving over several hours. The third wave was apparently the most powerful, arriving about an hour and a half behind the first one. Traveling at a speed of 620 mph, the tsunami reached Sumatra within 15 minutes, but other places had more time from the initiation until it reached their location. It took over 8 hours for the tsunami to reach Africa. By then warnings had been sounded and the death toll was small there.
But in other countries, the death toll was catastrophic. In Indonesia, it is estimated that 168,000 people died, along with 35,000 in Sri Lanka, 18,000 in India, 8,000 in Thailand, 269 in Somalia and as many as 600 in Myanmar. The total death toll is estimated at 229,866, making it one of the worst disasters in recorded history.
There was no warning system in the Indian Ocean when the tsumani struck, unlike the Pacific Basin, where tsunamis have been more common. Could such an event happen in the United States? Oh yes. Scientists warn that the collapse of a volcano in the Canary Island could generate a tsunami wave 100 feet high along much of the East Coast of the United States. Experts worry even more about the Pacific Northwest of the United States, where the Cascadia Subduction Zone threatens to produce an earthquake that could generate a massive tsunami off the coasts of Oregon and Washington.
Since the 2004 tsunami, NOAA has expanded its tsunami warning service to include not only the Pacific, but the Atlantic, the Gulf of Mexico, as well as Puerto Rico and the Virgin Islands. In addition, tsunameters were being deployed in the Indian Ocean.
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