December 11, 2008

Indonesian Coral Reefs Predict Large Quake Within 20 Years

Researchers reported Thursday that a study of reefs in Indonesia found that corals record cyclical events in the environment, and that these events could foretell a considerable earthquake in the eastern Indian Ocean within the next twenty years.

Scientists at the California Institute of Technology's Tectonics Observatory studied corals off Indonesia's Sumatra island, and found them to include annual growth rings, similar to those in tree trunks, which document cyclical events such as earthquakes.

"If previous cycles are a reliable guide we can expect one or more very large west Sumatran earthquakes ... within the next two decades," said Kerry Sieh, professor at the California Institute of Technology's Tectonics Observatory, at a press conference in Singapore.

Researchers said the earthquake could be similar to the magnitude 9.15 earthquake responsible for the disastrous 2004 Asian tsunami.  The tragedy left nearly a quarter million people dead or missing, more than 170,000 of which were in Aceh on the northwestern tip of Sumatra.

Sieh advised people in Sumatra to be prepared, but said Thailand and Sri Lanka were unlikely to be affected,

"The tsunami could be at five meters in Padang (in Sumatra). This is a worse case scenario," he said.

Sieh said corals off Sumatra's Mentawai Islands indicated a major earthquake had occurred every 200 years since the year 1300.

"When earthquakes push the seafloor upward, lowering local sea level, the corals can't grow upward and grow outward instead," said the researchers.

In a report published in the journal Nature earlier this month, Sieh and his team described an area off Sumatra that had been the source of devastating earthquakes, and said the area still held significant pent-up pressure that could spark another strong quake.

The current study was published in the journal Science.


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