Indian Ocean shores were stuck by tsunamis repeatedly during last 2,800 yrs

October 30th, 2008 - 12:33 pm ICT by ANI  

Chulalongkorn University

Washington, Oct 30 (ANI): Scientists have found evidence which indicates that the 2004 tsunami that inundated Indian Ocean coastlines, leaving behind a trail of destruction, was not a first-time occurrence, as the mega waves have repeatedly washed over a Thai island during the last 2,800 years.

The evidence was found by a research team, led by Kruawun Jankaew of Chulalongkorn University in Thailand, working on Phra Thong, a barrier island along the hard-hit west coast of Thailand.

The team unearthed evidence of at least three previous major tsunamis in the preceding 2,800 years, the most recent from about 550 to 700 years ago.

A second team found similar evidence of previous tsunamis during the last 1,200 years in Aceh, a province at the northern tip of the Indonesian island of Sumatra, where more than half the deaths from the 2004 tsunami occurred.

The team found evidence for previous tsunamis by digging pits and auguring holes at more than 150 sites on an island about 75 miles north of Phuket, a Thai tourist resort area ravaged by the 2004 tsunami.

That tsunami was generated 300 miles to the west when the seafloor was warped during a magnitude 9.2 earthquake.

At 20 sites in marshes, the researchers found layers of white sand about 4 inches thick alternating with layers of black peaty soil.

Witnesses confirmed that the top sand layer, just below the surface, was laid down by the 2004 tsunami, which ran 20 to 30 feet deep across much of the island.

Radiocarbon dating of bark fragments in soil below the second sand layer led the scientists to estimate that the most recent predecessor to the 2004 tsunami probably occurred between A.D. 1300 and 1450.

They also noted signs of two earlier tsunamis during the last 2,500 to 2,800 years.

According to scientists, sparse knowledge of the regions tsunami history contributed to the loss of life in 2004.

Few people living along the coasts knew to heed the natural tsunami warnings.

But, on an island just off the coast of Aceh, most people safely fled to higher ground in 2004 because the islands oral history includes information about a devastating tsunami in 1907.

A regions tsunami history can serve as a long-term warning system, Atwater said.

The research will reinforce the importance of tsunami education as an essential part of early warning, according to Jankaew, the lead author of the research.

This will be a big step towards mitigating the losses from future tsunami events, he said. This research demonstrates that tsunami geology, both recent and past tsunamis, can help extend the tsunami catalogues far beyond historical records, he added. (ANI)

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