September 5, 2007

Study: Tsunami Could Kill 1M in South Asia

BANGKOK, Thailand -- At least a million people in South Asia's Bay of Bengal could be swept to their deaths by a tsunami if a giant earthquake hits off the coast of Myanmar, according to a study published Thursday.

But the study's author, Phil Cummins, said he does not have enough data to say whether such a cataclysmic event would hit parts of Myanmar and Bangladesh in the next few decades or in several hundred years.

"I don't want to cause a panic. There is no reason anything like this would happen soon," said Cummins, of Geoscience Australia.

The threat of tsunamis has taken on added urgency in recent years after a massive earthquake off Indonesia's Sumatra island in December 2004 triggered a tsunami that killed more than 230,000 people and left a half million homeless in a dozen countries.

Cummins' study, which appears in Thursday's issue of the journal Nature, is the first time anyone has suggested that an earthquake off the coast of Myanmar could spawn a tsunami "that could have pronounced impact on the Chittagong coast and the Ganges-Bhramaputra delta at the northern tip of the Bay of Bengal," it said.

The numbers of people at risk from a tsunami, Cummins wrote, may be "over a million" given that the region is home to Bangladesh's second largest city of Chittagong and there are tens of millions living just above sea level.

Cummins has not presented his findings to the governments of Myanmar and Bangladesh. Officials from Myanmar and Bangladesh could not immediately be reached for comment.

The area Cummins studied is a section of the Sunda Megathrust that stretches all the way from Western Australia to the Himalayas. A rupture of the fault was blamed for the Sumatra earthquake in 2004.

Examining historical records, Cummins found evidence that an earthquake estimated at magnitude 8.5 to 9.0 struck off the western Myanmar coast in April 1762. He said it probably produced a tsunami, citing eyewitness accounts of waves washing over nearby Cheduba Island, submerged coasts near Chittagong and rising river levels as far inland as Dhaka.

He said future quakes and tsunamis were likely, given the historical accounts and more recent surveys of the area which determined a magnitude 8.5 quake would hit the area every 100 years and a 9.0 every 500 years.

"I would hope this spurs further work in confirming these past events," he said. "It should be possible to answer how big was this event, how often do these events occur and what kind of tsunamis are generated through further geological investigation."

The reaction to Cummins findings has been mixed, with some tsunami experts saying they shed important light on a section of Sunda Megathrust that has received little attention in the past.

"The main value of the paper is in advertising the danger of the section of the megathrust that no one has worried about," said California Institute of Technology's Kerry Sieh, who has used coral records and GPS networks to predict that a big quake and tsunami are likely to hit parts of Sumatra Island in the coming decades.

"His point is well taken. This part of the megathrust has produced a larger earthquake in the past and so it could do so in the future too," Sieh said. "The effects on the west coast of Myanmar and more importantly Bangladesh would be awful."

But Costas Synolakis, director of the Tsunami Research Center at the University of Southern California, said the possibly of a tsunami in the area was previously known and questioned whether the fault would rupture to the extent estimated by Cummins.

Synolakis also said in an e-mail interview that the scenario presented by Cummins "could lead to a massive panic south of Chennai (India) and possibly a sense of reassurance in Sri Lanka" where he said the threat of another tsunami was worse.


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Nature magazine: http://www.nature.com/nature