Coastal areas under risk of ‘local tsunami’

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The country is under the threat of a local tsunami that may originate in the subduction zone of neighbouring Arakan coast near the Bay of Bengal and it could cause massive destruction in the coastal areas of Bangladesh.

However, there is very low possibility of a local tsunami while more frequent transoceanic tsunami is unlikely to do any serious harm here as the velocity of the giant waves would weaken when they reach the coastal belt, experts said.

According to the seismic gap theory, subduction zone located in the Bay at the juncture of Indian plate and Eurasian plate may generate potential earthquake in near future.

The last tsunami in the region occurred in 1762 due to a 7.5 magnitude earthquake along the Arakan coast and now time is due for another massive undersea earthquake over there, they said.

At any moment, now or after several decades, a great undersea earthquake is going to occur that might generate tsunami in this region, experts said. But there will be little harm to the country’s coastal belt if the epicentre of the undersea earthquake remains as far away as Java-Sumatra, a most earthquake-prone area that has recently witnessed a number of earthquakes of different magnitudes, they said.

Recently the issue of tsunami risk for Bangladesh has become a much-talked issue among the geologists following an article written by Phil Cummins published in ‘Nature’ magazine about possible tsunami in the Bay of Bengal due to an undersea earthquake along the Arakan coast.

Leading geologists in the country said Bangladesh is under the risk of a local tsunami and it poses the threat of a massive disaster as there will be very little time to warn coastal inhabitants about the tsunami.

However, many factors have to work at the same time for occurrence of such tsunami, said the experts.

“If such a tsunami is caused, it would hit Bangladesh coast within 20 minutes and it would be dangerous for the country due to the vast extent of the low elevated coast plain,” said ASM Maksud Kamal, national expert, Earthquake and Tsunami Preparedness project.

Aftab Alam Khan, a leading geologist of the country, said, “Analysing the tectonic and geographic conditions of the Bay of Bengal, I find very low possibility of a tsunami here. But massive submarine landslide may occur due to earthquake in the Bay of Bengal what would be destructive for the country’s coastal belt due to sea turmoil.”

Inhabitants of coastal islands could be swept to death in case of any local tsunami, the two experts said.

However, any transoceanic tsunami originating in Java-Sumatra region or somewhere else would not harm Bangladesh, as the velocity of giant waves would weaken before reaching the country’s coastal zone, they said.

“Before reaching the country’s coast the velocity of the tsunami water column would reduce by hitting the sea slope lying as far as 100 kilometres from the shore. Then it would float over the sea shelf and when it reaches the coast the velocity of the waves would be so little that it would hardly do any harm in our coastal belt,” said Maksud Kamal.

Right now the country does not have any expertise to predict earthquake or tsunami.

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