Updated on Saturday, September 08, 2007, 00:00 IST

New York, Sept 08: The densely populated Bay of Bengal looks to be at risk from very large tsunami-producing earthquakes, suggests a paper published in Nature magazine this week.

Contrary to some previous studies, the plate boundary in this region is probably at sea, hidden below the thick layer of sediments in the Bengal fan, says the author, explaining that this means that a subduction-zone earthquake would be likely to generate a tsunami.

Evidence of a large earthquake in Myanmar's Arakan in 1762 also indicates an off-shore origin, the study says.

Phil Cummins, a seismologist at the National Geoscience Australia Agency in Canberra, is also quick to caution that his ideas need confirmation before "policymakers start doing anything".

The northern Bay of Bengal was formerly thought to be an unlikely place for large earthquakes that result when tectonic plates that are pushing against one another suddenly wrench, with one plate slipping below the other, The Nature said.

These 'megathrust' earthquakes can cause tsunamis, as water is suddenly displaced up and down by the thrusting rock.

The plate boundary further south off the coast of Sumatra causes such quakes -one of which created the devastating 2004 wave.

Previous research had hinted that further north, the plate boundary comes ashore in Myanmar rather than continuing up into the northern end of the Bay of Bengal, that the Indian Ocean plate is not subducting there and that the land beneath Myanmar is instead moving north with the Indian continental plate.

But the seismological and geological evidence for this is complex and open to interpretation.

Bureau Report