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Tuesday, 11 January, 2005

Satellite Measures Tsunami Waves

Tuesday, January 11, 2005 (Washington):

The tsunami that killed tens of thousands around the Indian Ocean was caught by a series of radar satellites.

This allowed National Oceanic and Atmospheric Administration scientists to develop measurements of the wave in mid-ocean.

While a tsunami can rise to great heights when it arrives at the shore, such waves are often barely noticeable in the ocean.

In this case, scientists found that two hours after the undersea quake that launched the tsunami, the wave was about two feet.

An hour and 15 minutes later it was down to about 41 cm. After eight hours the main wave was down to about 5 to 10 cms, though a portion in the Bay of Bengal was still at about 25 cm, according to the N0AA scientists.

Spreading wave

A massive earthquake deep beneath the ocean off Indonesia caused the tsunami by shifting the sea floor, resulting in displacement of the water overhead and causing a wave to spread out from that location.

Unlike surface waves that affect only a shallow amount of water, a tsunami stretches all the way to the sea floor and, as that rises to the land, so does the wave. Arriving at shore, such waves can grow suddenly by dozens of feet.

The satellite imaging did not provide a depth for the waves that hit ashore. The new measurements were based on data from four earth-orbiting satellites. Researchers hope the work will help them develop models to improve tsunami forecasts.

The data, which took several days to analyze, came from the TOPEX/Poseidon and Jason satellites operated by NASA and the French space agency, CNES; the European Space Agency's Envisat and the US. (AP)
Source : NDTV.COM (Website)
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