BANGLADESH IN GRAVEST THREAT OF EARTHQUAKE
Morshed Jahan Mithun
The massive 7.9 magnitude earthquake in Nepal and its climbing death toll have raised the heavyweight cautionary signal for Bangladesh about colossal earthquake.
After the massive quake that killed more than 3,000 people in Nepal, two tremors have hit Bangladesh on Saturday and Sunday. The country was jolted by a massive 7.5 quake on Saturday, causing panic among the people in the capital and parts of the country.
The magnitude of Sunday’s quake was 6.7 in Richter scale and the epicentre was 17km South of Kodari, Nepal, according to USGS.
Bangladesh, the country of more than 160 million people and the highest in the population density chart, is located on the world’s largest river delta. The country is close to sea level, which exposes it to tsunamis and the possibility of rivers jumping their banks in the event of earthquake.
Scientists have come to recognise that it sits at the juncture of several active tectonic plate boundaries–including the tail end of the one that caused the 2004 Sumatra tsunami that killed over 200,000 people, 1,300 miles south.
Syed Humayun Akhter, a seismologist at the Dhaka University Earth Observatory, warns that an earthquake near the crowded Dhaka could dwarf other modern tragedies.
Earth Institute blog published a brief documentation in 2011 where Syed made such caution after a research being jointly conducted by seismologists of Lamont Doherty Earth Observatory, Columbia University, USA the in conjunction with department of Geology, Dhaka University.
The research measured plate motions at six different sites of Bangladesh including Dhaka which clearly demonstrate that Dhaka is moving 30.6 mm/year in the direction northeast.
Further, the rate of strain accumulation is relatively high in and around Dhaka. It may precipitate in an earthquake of magnitude 6.8 in the event of the release of accumulated strain.
The shallow subsurface of Dhaka is also characterised by number of faults of variable dimensions.
These faults are vulnerable to motion where these coincide with the zones of high particle velocity.
Another study of Michigan University has pinpointed that Dhaka is one of the earthquake vulnerable city out of top cities because of its unplanned urbanisation.
Bangladesh lies in a seismically active zone making the occurrence of major earthquakes a realistic possibility.
Though Dhaka city lies in the moderate risk zone due to some others risk factor like high population density, unplanned urbanisation and lack of open spaces, the city is most vulnerable than any other parts of Bangladesh.
The country geographically located close to the junction of two subduction zones created by two active tectonic plates: the Indian plate and the Eurasian plate.
Moreover, the country is surrounded by the Himalayan Arc, the Shillong Plateau and the Dauki fault system in the north, the Burmese Arc and Arakan Yoma anticlinorium in the east, and the Naga Disang Haflong thrust zone in the northeast.
The existence of an active fault had been proved in Haluaghat of Mymenshingh, adding further risk to the vulnerability, experts expressed after 2011 tremor.
In September 2011, 11 million Dhaka dwellers roughly were rocked by three earthquakes each registering at least six on the Richter scale – but without any casualties or damage, according to the Bangladesh Meteorological Department.
The department said the most recent quake in September did not cause casualties due to “sheer luck” because the tremor stopped in less than two minutes.
In a “worst-case scenario”, more than 100,000 people may die and numerous others need hospitalisation if a 7.5 magnitude earthquake from the nearby Madhupur Fault were to hit the capital, according to a 2009 study by the Comprehensive Disaster Management Programme (CDMP) under the Ministry of Food and Disaster Management.
Some 400,000 buildings in the country’s three largest cities – Dhaka, Chittagong some 200km south of Dhaka, and Sylhet in the northeast – are extremely vulnerable to earthquakes and would be damaged “beyond repair” in the event of a major quake, the CDMP study said.
A strong earthquake of 8.6-magnitude occurred in Assam on August 15 in 1950, killing 1,526 people. Another 8.1-magnitude quake hit Assam on June 12 in1897, killing 1,500 people.
The casualties were less because of low density of population and fewer numbers of concrete structures at that time.
‘Sheer luck’ does not walk on same way as earthquake cannot be prevented. But certainly it is the high time to be much more concerned about the probable impending earthquake in order to minimise the loss of lives and property for national interest.
APRIL 27, 2015