The 2004 tsunami killed 230,000 people and left half a million homeless in 12 countries. But a new one could be four times more disastrous, killing over a million people in South Asia's Bay of Bengal, but its date cannot be precisely predicted: it could strike Myanmar and Bangladesh in the next few decades or in several centuries.
"I don't want to cause a panic. There is no reason anything like this would happen soon," said author Phill Cummins, of Geoscience Australia.
It's the first time an earthquake off the coast of Myanmar is predicted to trigger 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. The numbers of people at risk from a tsunami 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," said Cummins, who has not presented his results to the governments of Myanmar and Bangladesh.
The investigated area is part of the Sunda Megathrust, stretching from Western Australia to the Himalayas, and the 2004 earthquake off Sumatra island that triggered the killer tsunami occurred here.
Historical records show that an earthquake of a magnitude of 8.5 to 9.0 hit off the western Myanmar coast in April 1762 and eyewitness described tsunami wiping out nearby Cheduba Island, submerging shores near Chittagong and rising river levels as far inland as Dhaka.
"Future quakes and tsunamis are likely, given the historical accounts and more recent surveys of the area which determined a magnitude 8.5 quake will 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. 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." said Cummins.
"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.
"This part of the megathrust has produced a larger earthquake in the past and so it could do so in the future too. The effects on the west coast of Myanmar and more importantly Bangladesh would be awful." said Sieh.
A possible new tsunami has been forecast by other experts, too, the question is if it will have the magnitude predicted by Cummins.
The new scenario "could lead to a massive panic south of Chennai (India) and possibly a sense of reassurance in Sri Lanka", said Costas Synolakis, director of the Tsunami Research Center at the University of Southern California.