Bangladesh has not seen an earthquake this deadly in more than two decades
When a 5.7-magnitude earthquake struck near Narsingdi just outside Dhaka on Friday morning, buildings cracked, stairwells filled with panic and at least 10 people died -- crushed by falling masonry, railings and walls, or as they tumbled from trees and upper floors.
For Prof Mehedi Ahmed Ansary, who teaches civil engineering at the Bangladesh University of Engineering and Technology (BUET), the damage from what was, in global terms, a moderate tremor is itself the message.
"What we saw today at magnitude 5.7. Imagine what happens at magnitude 7," he told bdnews24.com.
"Buildings will collapse, casualties will soar. If a major earthquake strikes within 100km of Dhaka, 200,000 to 300,000 people could be killed or injured, and around 35 percent of the city's buildings could collapse."
Warning the government in unusually blunt terms, he described Friday's jolt as "a foreshock, one of the smaller earthquakes that comes before a big one".
The earthquake should serve as a wake-up call for authorities to brace for an even stronger quake in future, he said.
Seismologists have long feared that a powerful quake is overdue on the major tectonic faults that ring Bangladesh. They now warn that a strong shock within 100km of the capital could leave 500,000 to 700,000 people trapped under rubble and cut off, in addition to the mass casualties.
They argue that while a major earthquake cannot be prevented, its toll can be reduced: by assessing building quality, classifying structures by risk, warning residents, and conducting regular drills.
"Buildings need to be checked right away. Dhaka's buildings, in particular, need immediate attention," Prof Ansary said, drawing attention to potential damage that a powerful earthquake could unleash in the densely populated capital, where building codes are often ignored in construction.
Friday's tremor was the strongest felt in Bangladesh in decades. As of Friday, at least 10 deaths had been reported in three districts -- Dhaka, Narsingdi and Narayanganj-- and more than 600 people injured.
WHY A 'WAKE-UP CALL'
Syed Humayun Akhter, a retired professor of geology at Dhaka University and long-time head of its seismological observatory, has spent decades mapping the country's vulnerabilities.
He says Bangladesh's fate is written in the slow collisions of the tectonic plates beneath it. Earthquakes, mountains and volcanic eruptions, he notes, are all controlled by the movement of the Earth's crustal plates.
The outer shell -- the 70-100 km-thick lithosphere -- is broken into 13 major plates, floating and grinding against each other atop the hotter, softer asthenosphere. To Bangladesh's north lies the junction of the Indian and Eurasian plates; to the east, the boundary between the Indian and Burmese plates.
"This earthquake occurred on the contact between the Indian and Burma plates, which runs from the Haor wetlands of Sunamganj and Kishoreganj down under the Jamuna river," Prof Akhter said. "The epicentre was on the north-eastern corner of that junction."
He believes a vast amount of strain is still locked in that system.
"Energy equivalent to an 8.2-magnitude earthquake is still stored there," he warned. "At any time we could see an earthquake of that size or even larger."
Calling Friday's tremor a "wake-up call" ahead of a larger event, he said: "The locked zone has started to unlock. The plates were stuck together. Now they are beginning to slip."
BUET's Prof Ansary drew the same conclusion. "At 5.7 we saw this level of damage," he said. "At magnitude 7 the destruction will be far greater. Buildings will collapse, the death toll will rise sharply."
Experts have long cautioned that because Bangladesh lies at the junction of two plates, it faces a high risk of powerful quakes. Changes in river courses and heavy alluvial soils add to the danger in many regions.
WHAT HISTORY TELLS US
Prof Ansary's research suggests the region typically experiences magnitude-7 earthquakes roughly every 150 years and magnitude-8 events every 250-300 years.
Between 1762 and 1930, he notes, several quakes between 7.0 and 8.5 are recorded in the historical and geological record.
Speaking to bdnews24.com previously, he said: "In the last 100-150 years there has been no major earthquake in this region. At any time we could see a magnitude-7 event. An 8.0 is not expected yet. But between 2020 and 2030 a major earthquake will come."
Recent data point to mounting activity. In Bangladesh and its surroundings there were 27 recorded earthquakes in 2021, 19 in 2022, 35 in 2023 and 54 in 2024.
Of these, nine quakes in 2021 had their epicentres within Bangladesh; in 2023, seven did, with two more on the India-Bangladesh border.
In 2024, 13 earthquakes originated inside the country. There were none with epicentres in Bangladesh in 2022.
Most recent tremors have ranged from magnitude 2.8 to 6.0.
"The last major earthquake in this region was an 8.1 in 1897," Prof Ansary said. "We expect this level of risk to recur every 250-300 years."
Since 1930, there has been no truly large event, but research suggests the underlying risk remains.
WHERE THE GREATEST DANGER LIES
On the basis of geological structure, Prof Akhter points to two major active faults inside or along Bangladesh.
One is the Dauki Fault along the Sylhet-Meghalaya border and the other is the Sitakunda-Teknaf Fault, which runs down the Chattogram coast.
In addition, he says, "There are countless fractures across the Chattogram Hill Tracts and the plains which could generate earthquakes."
"Dhaka is encircled by faults to its east, west, north and south," he added.
A 2016 study he co-authored warned that a powerful "subduction zone" earthquake, where one plate dives beneath another, could be generated any time along the boundary between the Indian and Burma plates.
The zone, which runs offshore under the Bay of Bengal, has enough stored energy to produce a magnitude 8.2-9.0 quake, with the energy building up from the subduction interface to Chattogram.
"The series of small quakes we've been seeing are signals that the stored energy is trying to escape," he said.
Dhaka, with its dense, unplanned sprawl of concrete, would bear the brunt of any such event.
Bangladesh has been divided into three seismic risk zones. The north-eastern region is categorised as Zone 1, the highest-risk area; the central belt, including Dhaka, is Zone 2 with moderate risk; and the south-west is Zone 3, relatively less vulnerable.
A joint survey by the Comprehensive Disaster Management Programme (CDMP) and Japan's JICA in 2009 projected that a magnitude-7 or greater earthquake affecting Dhaka could cause 72,000 buildings to collapse outright and damage another 135,000.
Chattogram and Sylhet are also at high risk. A 2011 study by the Chattogram University of Engineering and Technology concluded that 78 percent of buildings in the port city were vulnerable.
Analysts believe this ratio has changed little in the one and a half decades since.
A COUNTRY ON A FAULTLINE, A CITY IN THE CROSSHAIRS
"Bangladesh is not among the most earthquake-prone countries in terms of frequency," Prof Akhter said. "But in terms of risk, it ranks very high."
"Given the amount of energy stored at the junction of the Indian and Burma plates, if it is released we could see an earthquake between magnitude 8.2 and 9.0.
"It might happen tomorrow, it might happen 50 years from now. We cannot say when. But when it comes, it will be devastating. Earthquakes on subduction zones are particularly violent."
The Bangladesh Meteorological Department's Seismic Observation Centre measured Friday's quake at 10:38am, with a magnitude of 5.7 on the Richter scale. The epicentre was about 13 kilometres from Dhaka, at a depth of 10 kilometres.
Prof Akhter, noting the proximity, said: "In living memory we have not seen such a strong earthquake at a distance of just 30-40 kilometres from Dhaka. Several generations have never experienced shaking like this."
So far, four deaths have been confirmed in Dhaka, five in Narsingdi, near the epicentre, and one in Narayanganj.
In Old Dhaka's Armanitola, three men, Rafiqul Islam, Haji Abdur Rahim and his son Mehrab Hossain Rimon, were killed as bricks and plaster sheared off the walls and cornices of a high-rise. In Mugda, construction guard Maksud -- identified with a single name -- died when a railing fell from the roof of an under-construction building.
In Narsingdi, the dead include Delwar Hossain Ujjal, 40, and his 8-year-old son Hafiz Md Omar, from Gabtali in Chinishpur Union; Kazem Ali Bhuiyan, 75, of Malita Paschimpara; Nasir Uddin, 65, of Kazirchar Nayapara; and Forkan Mia, 45, of Ajkitola in Joynagar Union.
In Rupganj, Narayanganj, the collapse of a wall killed a 10-month-old baby and injured the child's mother and one other person.
In Gazipur, more than 400 workers were injured as they rushed out of factories in panic. "People came in with varying degrees of injury from all over the area," said Dr Abdul Salam Sarkar, deputy director of Shaheed Tajuddin Ahmad Medical College Hospital.
In Narsingdi, more than 100 people were injured, three of the most seriously hurt were transferred to Dhaka Medical College Hospital for treatment.
At Dhaka University, three students injured themselves after jumping from the third floor of Haji Muhammad Mohsin Hall and the fourth floor of Muktijoddha Ziaur Rahman Hall. Others were injured on the stairs as they fled.
Beyond the deaths and injuries, cracks have appeared in countless buildings across Dhaka and other cities, with plaster falling and some structures left visibly leaning.
At Ghorashal Power Station in Narsingdi's Palash Upazila, a fire broke out, burning part of the substation and cutting power to the national grid. The Power Development Board said there were interruptions to electricity generation in several places. Mobile phone networks also experienced brief outages.
HOW TO SURVIVE AN EARTHQUAKE
Experts set out simple rules that can mean the difference between life and death when the ground begins to shake:
* At the first tremor, try to move to an open space. As you head for the exit, warn others if you can and, if time permits, switch off electricity and gas. Do not waste time trying to gather belongings.
* If you cannot leave the building, and it is brick or reinforced concrete, shelter in a corner; in frame structures, take cover at the base of a column.
* Avoid excessive movement. Rushing for the stairs, running outside or jumping from windows greatly increases the risk of injury. The more you move, the more danger you create.
* Follow the "drop-cover-hold on" method recommended by the American Red Cross. Drop to the ground, take cover under a sturdy table or desk, and hold on. Choose a piece of furniture you can move with if necessary.
* Well-built, earthquake-resistant buildings rarely collapse. Most casualties occur when objects and furniture fall. That is why it is vital to get under something solid.
* Never use lifts during a quake.
* If you are in a car, stay inside with the doors closed. Outside, you risk being hit by falling debris.
* Be aware that "foreshocks" and "aftershocks", smaller quakes before and after the main shock, can also be dangerous. Aftershocks can begin within an hour and continue for days. Stay alert.