Small tremors a wake-up call for impending mega quakes

The recent spate of small-scale earthquakes, including today's 5.6-magnitude tremor that shook Dhaka and other parts of the country, could be a precursor to a powerful 8.2-9 magnitude earthquake that could cause widespread destruction, experts warn.

They say mega cities such as Dhaka and Chattogram could become significant disaster zones in the event of powerful earthquakes, given their high population density and unplanned development.

To mitigate potential damages, they recommend that the government take preemptive actions, including raising awareness and enforcing stringent building codes.

Around 200 garment workers in Chauddagram, Cumilla, sustained injuries as they hurriedly exited a factory in panic during the earthquake. Additionally, a student from Dhaka University's Masterda Surja Sen Hall was injured while jumping from his first-floor room window.

Besides, cracks appeared in three halls at the Cumilla University, and the plaster of a hall at Dhaka University collapsed due to the tremor.

Many Dhaka residents came out on the streets in fear during the tremor. People took to social media to report the jolt in parts of Bangladesh.

With today's tremor, Bangladesh has witnessed six earthquakes with over magnitude 5 this year.

The region of Bangladesh experiencing recent earthquakes, stretching from Sylhet to Chattogram to Cox's Bazar and surrounding areas, is known as a "subduction zone." This region has accumulated significant strain energy due to the absence of major earthquakes for around a thousand of years, said Dhaka University's geology department chairman Dr Syed Humayun Akhter.

"Our research indicates that the accumulated energy in this region could trigger an earthquake of magnitude 8.2 to 9, which could occur at any time, ranging from today to 50 years from now. This earthquake could happen either as a single, massive event or as a series of tremors," he said.

The epicentre of Saturday's tremor which hit the country at 9.35am was located 10km east-northeast of Lakshmipur's Ramganj upazila, according to the United States Geological Survey (USGS).

Ramganj is situated within an earthquake subduction zone as well, said Dr Akhter.

The USGS says the magnitude of yesterday's tremor was 5.5, while the German Research Centre for Geosciences says it was 5.8.

However, according to the Bangladesh Meteorological Department, the magnitude was 5.6.

The maximum intensity of the quake was "VIII or Severe" on the Modified Mercalli Scale and based on scientific estimates by the US Geographic Survey (USGS),  this level can cause moderate to heavy damage.

Wake up call for Dhaka

Dr Syed Humayun Akhter said if a magnitude 8 earthquake occurs in any part of this subduction zone, the potential for greater damage in Dhaka compared to the epicentre vicinity is significant. This heightened risk in Dhaka is attributed to its dense population, poor urban planning, and the government's inadequate preparedness.

The consequences could worsen by unregulated urbanisation in both Dhaka and Chattogram, leading to the construction of structurally weak buildings that could collapse during an earthquake, he said.

Additionally, the presence of design flaws in some structures increases the likelihood of collapse. Urgent measures should be taken to prepare for and mitigate the potential impact of a major earthquake in these areas, Dr Akhter said.

He emphasised the need for prioritising planned urbanisation to avert significant disasters. The primary objective should be to undertake initiatives aimed at raising awareness, as this represents the most practical and feasible solution.

He highlighted the utmost importance of prioritising building code compliance in the construction of new buildings.
RMG workers injured in Cumilla

Most of the damages reported in Saturday's earthquake was in Cumilla, the neighbouring district of Lakshmipur where the epicentre of the earthquake was located.

Over two hundred garment workers in the district's Chauddagram were injured while trying to evacuate the factory building of Amir Shirt Garment Limited during the earthquake. Many of the injured were admitted to the upazila health complex.

Chauddagram upazila Health Officer Golam Kibriya said, "The exact number of admissions is not yet clear, but it is believed to be over two hundred."

Anwar Hossain, manager of Amir Shirt Garment Limited, said, "Most of our workers safely evacuated during the earthquake. Suddenly, someone in the crowd shouted that the building had developed cracks. This caused panic among the female workers, leading to a rush that resulted in several injuries."

Meanwhile, cracks emerge in three residential halls at the Cumilla University including Kazi Nazrul Islam Hall, Bangabandhu Sheikh Mujibur Rahman Hall, and Nawab Faizunnissa Chaudhurani Hall.

Emran Hossen, resident student at Bangabandhu Sheikh Mujibur Rahman Hall, said, "During the earthquake, we were unable to descend to the lower floors. Following the tremors, we observed a slight elevation in two tiles on the upper side of the corridor in the south block."

On the other hand, no major damages were reported in Lakshmipur, the district with the epicentre of the earthquake. However, some buildings, including the minaret of a mosque, did exhibit cracks.

Dhaka University student jumped from window

According to media reports, the plaster of Dhaka University's Haji Muhammad Mohsin Hall collapsed during the tremor. The glass door of the reading room within the hall also shattered. The seismic event caused panic among students, leading to a rush for safety in other residential halls of the university.

A student attached with Masterda Surja Sen Hall sustained injuries while jumping from the second floor in fear during the earthquake.

The student, identified as Minhajur Rahman, is enrolled in the Department of Islamic History and Culture. Following the incident, he was taken to the Dhaka Medical College Hospital for treatment.

Recent earthquakes in Bangladesh

On 2 October, the country experienced a 5.4 magnitude earthquake originating from Sherpur at around 6:45pm. On 11 September, Sylhet was struck by another earthquake measuring 5 in magnitude. Another seismic event of 5.3 magnitude shook Sylhet on 14 August.

The country felt the impact of a 5.0 magnitude earthquake originating from Golapganj in Sylhet, affecting Dhaka and other districts on 16 June. The first seismic activity recorded this year was on 23 January with a 5.1 magnitude earthquake originating in Sylhet.

Earlier in 2022, Bangladesh encountered three earthquakes surpassing a magnitude of 5 Richter scale.

According to earthquakelist.org, the strongest recent earthquake of the past 10 years near Bangladesh occurred on 4 January 2016 05:05am with a magnitude of 6.7 and struck 180 kilometres east of Sylhet, at a depth of 55 km.