The city of Dhaka may face a devastating earthquake anytime due to shifting of the present plate boundary to the Jamuna-Meghna river basin from east and rapid accumulation of seismic energy beneath the city.
“With the passage of time, the present plate boundary is shifting from east to west (Jamuna-Meghna river basin), which put Dhaka at risk of tremor,” said seismic expert Prof Dr Syed Humayun Akhter, showing the seismic model of Dhaka University Earth Observatory.
He said Dhaka is also more vulnerable to earthquake due to its geological location while the city is located near the three active faults – Madhupur, Dawki and Himalayan faults.
“Madhupur fault located near Dhaka city is very active to generate a moderate to heavy earthquake. A big earthquake originated from the fault in 1885 (127 years ago). Now energy is being accumulated in this fault and small quakes are giving an indication of a bigger one,” said Dr Syed Humayun, a professor of Geology Department of Dhaka University.
Showing data of earthquake, he said a 4.5 magnitude tremor originated from Madhupur fault at beneath the Buriganga River on December 19 in 2001 while two more small quakes occurred from the fault in 2008 (epicenters – Manikganj and Mymensigh).
“That means Madhupur is an active fault. And when energy accumulation will reach a critical level, the energy will be released leading to a devastating quake from the fault that will critically affect Dhaka city,” he said.
According to the seismic experts, a powerful earthquake needs at least 100-150 years to originate in a particular region and in that sense it is overdue for Bangladesh and parts of Assam, as 112 years have already passed since a heavy tremor from Dawki Fault (near Sylhet) hit the region. So, Dhaka and Sylhet are highly vulnerable to a powerful earthquake originating from Dawki fault.
Dr Syed Humaun said that if a heavy tremor occurs from Dawki fault, it will not only damage the Sylhet city, but will also badly affect capital Dhaka.
About the Himalayan fault, he said a huge energy has accumulated in the Himalayan fault and if an 8-magnitaute of earthquake originates from the Himalayan belt, Dhaka will experience massive loss and damage.
Referring to the model of Dhaka University Earth Observatory, the seismic expert said that the present plate boundary is shifting two millimeter per year in plain land while five millimeter in Chittagong belt and seven millimeter in Dawki fault.
“We’ve not yet calculated how much energy is accumulated in these faults because many factors are needed to calculate it. But energy accumulation in these faults almost reached mature level to generate tremors,” he said,
A government study in 2010 revealed that some 78,323 buildings will be destroyed completely if a 6-magnitude earthquake shakes Dhaka originating from Madhupur Fault, causing havoc in the densely populated capital city.
In case of a 7.5-magnitude earthquake originating from Madhupur Fault (near Dhaka city), some 72,316 buildings in the capital will be damaged totally and 53,166 others partially. If an 8.5-magnitude tremor from the plate boundary of Fault-2 hits the region, some 238,164 buildings will be destroyed completely across the country.
The government study says some 131,029 people will die instantly while another 32,948 will be injured needing hospitalization if a 7.5 magnitude earthquake from Madhupur Fault jolts the city.
There will be an economic loss of about US$ 1,112 million for only structural damage in case of a 7.5-magnitude earthquake from the Madhupur Fault. Economic loss due to damage of structures will be US$ 650 million and US$ 1,075 million respectively in case of an 8-magnitude earthquake from the plate boundary-2 and in case of a 6-magnitude earthquake from under Dhaka city, according to the study conducted by Comprehensive Disaster Management Programme (CDMP).
Although Dhaka is less vulnerable to tremor than Sylhet and Chittagong, it will experience massive damage due to soft formation of soil if one moderate quake hit the capital city, earthquake expert Prof Jamilur Reza Chowdhury told UNB.
“Unplanned urbanisation and construction of buildings filing up the low lying areas and wetlands intensify the earthquake risk for Dhaka city,” he said.
Prof Chowdhury said there are a large number of vulnerable buildings in the capital city. “One earthquake hit the city in 1897. If another hits the city again, over 100,000 people will be killed instantly amid collapse of the vulnerable buildings.”
Source: UNB Connect