The recent series of earthquakes in the country indicates that the energy locked deep within the subduction zone - a place where one giant slab of the Earth's crust slides beneath another - is trying to be released, increasing the risk of a major earthquake, especially in Dhaka and the surrounding areas, experts said.
On Thursday, a 3.6-magnitude earthquake occurred at 4:15pm at Ghorashal in Narsingdi, said Farzana Sultana, an assistant meteorologist at the Bangladesh Meteorological Department (BMD).
It was the seventh tremor since a 5.7-magnitude earthquake that occurred on the morning of 21 November, which had its epicentre 25 km from Dhaka in Madhabdi, Narsingdi. The tremor, with a depth of 10 km, was the strongest in the recent series of quakes.
Last Friday (21 November) and the following Saturday, four quakes were felt in Dhaka and nearby areas within a span of about 31 hours.
Major earthquake possible within months or decades!
Earthquake specialist and retired Dhaka University Prof Syed Humayun Akhtar said two tremors were felt in Sylhet and Cox's Bazar's Teknaf areas on Thursday.
This area lies at the junction of the Burma Plate and the Indian Plate - the subduction zone - which is vast. The tremors felt in Sylhet and Teknaf also fall within the same subduction zone.
Prof Humayun said the region has two main sources of seismic activity: the Dawki Fault in the north, and the Madh upur Fault plus the subduction zone to the east.
He said, "In our region, we mainly have the connection between the Indo-Asia plates. The part of the Indian plate that is moving beneath our plate forms a subduction zone. It starts from Sunamganj and Kishoreganj, runs along the Meghna River, and moves southward into the Bay of Bengal, just west of Teknaf. If you imagine a line there, the eastern side is the Burma Plate, and the Indian Plate is sinking beneath it. That sinking region is the subduction zone."
According to him, the Sylhet-Chattogram-Cox's Bazar region did not experience any major earthquake in the last thousand years. Before that, energy had been released and the "clock was reset." Since then, seismic stress has been rebuilding for centuries.
This pent-up energy can be released anytime - today, tomorrow, or decades later - but the longer it takes, the stronger the eventual earthquake will be. "There is no alternative to this. We have been warning about this for 10 years," he said.
He also said, "The 5.7-magnitude quake on 21 November occurred very close to the plate boundary. The next day's tremor was 5-10 km north of that same junction. Thursday's tremor also occurred within the same area, just 5-10 km from the boundary."
These events show that the accumulated energy is trying to break free, but the plates remain tightly locked. The 21 November quake likely created a tiny opening - a "test path" - through which some energy escaped. Now more small quakes in that area indicate that the pathway is widening, he said.
"As a result of this, a major earthquake of magnitude 7 to 8 could strike in the coming months or years, and, if it hits that zone, Dhaka will be the most affected city," he said.
Low preparation threatens to worsen high-risk factors
Prof Syed Humayun Akhtar said Dhaka sits at the "extreme peak of seismic vulnerability." All the risk factors are present: very high population density, weak and poorly regulated infrastructure, low earthquake resilience, high fire risk from electrical and gas line ruptures, and potential water-supply failures.
He stressed that only proper preparedness can minimise potential losses. Immediate priority should be short-term measures - especially raising public awareness.
He said that initiatives like Natural Disaster Day, earthquake drills, and capacity-building to boost people's confidence so they remain calm during quakes are essential. Without this, psychological trauma could last months or years for many.
He said the 5.7-magnitude earthquake on 21 November felt at 10:38am was the most severe earthquake in Bangladesh's recent memory. "We have never felt such intensity at the surface before. Naturally, residents of Dhaka became extremely frightened."
Dr Mehedi Ahmed Ansary, a specialist in geotechnical-earthquake engineering at the Bangladesh University of Engineering and Technology (BUET), also criticised the lack of official action.
"The government should call an urgent meeting with all stakeholders, including experts. I don't see any activity by the government," he said.
"The government said they were observing the situation but they lack the capacity to properly observe it," he said.
He said a national disaster advisory council was formed but it was dissolved after only a few meetings. "Maybe bureaucrats don't want it. I was part of it, but now the government doesn't call us," he said.
Dr Ansary warned that while there were numerous committees, plans and standing orders on disaster, "none are currently in action."
He stressed that immediate priority should be given to inspecting building safety by both authorities and residents themselves.
The Rajdhani Unnayan Kartripakkha (RAJUK) has assessed the earthquake resilience and risk of only 3,252 structures out of 21 lakh buildings in Dhaka and Gazipur so far, said an official.
At a recent meeting in the capital, RAJUK Executive Engineer Khandaker Md Wahid Sadiq said using the FEMA-310 guideline for seismic evaluation, they conducted rapid visual assessments of 2,705 educational institutions, 207 hospitals, 36 police stations, and 307 other buildings.
Of them, 579 buildings, including 568 educational institutions, five hospitals, three fire stations, and three other buildings have completed the Preliminary Engineering Assessment (PEA).
Only 187 buildings, including 94 schools, 78 colleges, 11 universities and four hospitals, have undergone the Detailed Engineering Assessment (DEA) for which RAJUK has recommended retrofitting.
RAJUK has also recommended the demolition of 42 buildings in Dhaka and Gazipur due to high seismic risk, said the official.
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