What message did the morning earthquake convey?

There are some geological cracks around Dhaka that control small and narrow rivers and canals in the area. The earthquake that jolted the city early on Friday is believed to have occurred due to such a crack.

ASM Maksud Kamal, a seismologist and pro-vice chancellor (VC) of Dhaka University, expressed this view in a conversation with Prothom Alo.

A mild quake shook the capital city at 5:57 am on Friday. According to the United States Geological Survey (USGS), the earthquake had a magnitude of 4.3 on the Richter scale with its epicenter in Dohar, 14 kilometers away from Dhaka. Its origin was 10 km below the surface.

Maksud Kamal said, “There are several small rivers in Dohar and its surrounding areas that are controlled by the (geological) faults. Such cracks may result in mild earthquakes. In geological terms, this earthquake process is called 'neotectonic'.”

The professor of disaster science and climate resilience department also said, “The morning quake was part of this neotectonic process. Generally, large-scale quakes do not occur from neotectonic faults. It's like what happened this morning.”

Maksud Kamal believes that the Ichamati River or any of its branches or canals could be the source of today's earthquake. He said the origin was 10 km below the surface. It implies that the quake originated from a shallow source. No large-scale quake happens from a shallow source caused by neotectonic cracks.

Seismologist Maksud Kamal further said, “From my study, the message about today's quake is that such earthquakes have happened in the country before. When an earthquake originates from the faultline that controls the river route, there is no fear of the quake being large-scale.”

He also noted that the region has had two major earthquakes so far – one in 1918 in Srimangal and another in 1885 in Manikganj, near Dhaka. The second one is called the 'Bengal Earthquake'.

Besides, there have been many small earthquakes. The morning quake was a similar one.

Recently, a study by some teachers from Columbia University and Dhaka University has identified 13 areas in Bangladesh as being at risk of earthquakes. The risk is severe for three hill districts and the Jaintapur area in Sylhet. All the risky zones are located at least 100 km away from the capital city.

Meanwhile, the Rajdhani Unnayan Kartripakkha (Rajuk) said in a study that Dhaka is also at risk of earthquakes. The public agency carried out the study throughout a period of four years, from 2018 to 2022.

According to the survey report, there are fault lines under the ground in Madhupur, Tangail. If there is an earthquake with a magnitude of 6.9, some 865,000 buildings will collapse in Dhaka. On the other hand, a 7.1 magnitude quake along the Dawki fault line in Sylhet would demolish at least 40,935 buildings in Dhaka.

The meteorological department has divided Bangladesh into three earthquake zones – highly risky (red), moderately risky (pink), and low-risk areas (yellow).

According to the department, Sylhet and Mymensingh regions are at high risk of earthquakes, along with Rangpur, Dhaka, Cumilla, and some parts of the Chattogram hill tracts.

Chattogram, Bandarban and Cox's Bazar districts, along with parts of Dhaka, Manikganj, Narayanganj, Munshiganj, Cumilla, Chandpur, Feni, Noakhali, Pabna, Sirajganj, Naogaon, Rajshahi, Natore, and Chapainawabganj are at risk of moderate earthquake. 

The entire Khulna and Barisal divisions in the southern region are at low risk of earthquakes.