Geology: Potential tsunami risk in the Bay of Bengal
A potential for giant earthquakes in the Bay of Bengal could expose a large and vulnerable population to a significant tsunami hazard. The study combines recent geological and geodetic data with an account of an historical earthquake in the region to produce a simulation of the tsunami that may have accompanied it.

It is now recognised that another large earthquake is likely to occur off central Sumatra, just east of the 2004 Sumatra–Andaman earthquake location. But there has been little concern about the subduction zone to the north, in the northern Bay of Bengal along the coast of Myanmar and Bangladesh.

Phil R. Cummins reviews observations from GPS and geological data which indicate that, 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. This means that a subduction-zone earthquake would be likely to generate a tsunami. Evidence of a large earthquake in Arakan in Myanmar in 1762 also indicates an off-shore origin. Local reports at the time describe how the river at Dhaka rose suddenly and drove boats ashore, and there is evidence of 3 to 7 metres of uplift along the coast.

The author’s tsunami simulation for this earthquake depicts the severe impact such an event might have today on this low-lying area that is home to over 60 million people. He concludes that the next giant earthquake may not be as large as in 1762 and may not occur for another 200 years, but a smaller event could occur sooner, threatening this heavily populated region.

CONTACT

Phil R. Cummins (Geoscience Australia, Canberra, Australia)

Please contact the author through:
Chris Thompson (Communications Section, Geoscience Australia, Canberra, Australia)

Tel: +61 2 6249 9642; E-mail: chris.thompson@ga.gov.au