Six earthquakes in three months, how worrying is this 

In the last three months, six earthquakes have been recorded in the country, including the recent Monday evening earthquake. Three of these seismic events occurred in September, while two took place in August.

Notably, two out of the six earthquakes were traced back to the Dauki fault, a significant fault line in the region. Bangladesh is characterized by two major epicenters, with the Dauki fault being one of them. The Dauki fault has been a recurring site for earthquakes over the past several years, experiencing a series of seismic activities. 

Experts hold differing opinions on the potential consequences of these small earthquakes on the Dauki fault. 

The epicenter of the earthquake felt on Monday was in the Meghalaya state of India. However, this area is not part of the Dauki fault; it falls within the Oldham Fault. 

ASM Maksud Kamal, a professor at Dhaka University's Disaster Science and Climate Resilience Department, informed Prothom Alo that Monday's earthquake did not originate from Dauki, which is typically the epicentre of most earthquakes in Bangladesh. Instead, it originated from the fault responsible for the significant Meghalaya earthquake in 1897, which had a magnitude of 8.3. Following that event, there were no major earthquakes in the region. 

However, despite the source of this recent earthquake not being Dauki, the successive occurrence of earthquakes has instilled fear in the region. 

In addition to Dauki, another source of earthquakes in the country is a subduction zone that extends inland from Sylhet to Teknaf. This region is where one tectonic plate subducts another plate. There are several sub-fault of the active main fault across the region. 

Maksud Kamal told Prothom Alo, "The Dauki fault spans 300 kilometres. Studies indicate that the interval between major earthquakes here is about 300 years. Accordingly, the Dauki fault may not pose an immediate threat, although there are differing opinions on this." 

What do the small earthquakes on the Dauki fault indicate? There are two explanations for this. A group of scientists believes that the occurrence of small earthquakes suggests that the immense energy stored in this fault is slowly eroding, reducing the risk of major earthquakes. 

Another group thinks that the energy is shifting through related nearby faults (sister faults) or floating fault lines via these small earthquakes. The strength of the original fault line remains intact. It does not imply that the strength of the main fault line is decreasing. 

Professor Maksud Kamal stated, "I am in support of the second opinion." 

Last September, the country experienced three earthquakes. On 17 September, an earthquake with a magnitude of 4.2 on the Richter scale was felt in various parts of the country, including Dhaka. Its epicentre was in Tangail, 59 km northwest of Dhaka. 

Earlier, on 11 September, an earthquake was felt in the Sylhet region with its origin at the Indo-Myanmar border. Additionally, on 9 September, another earthquake was felt, originating from the Cachar region of Assam, India. 

Bangladesh experienced two earthquakes in August. The first earthquake was felt on 14 August, with its epicenter in the Kanaighat area of Sylhet on the Bangladesh-India border. The second earthquake occurred on 29 August and originated in Sylhet as well. Notably, the epicenters of both August earthquakes were situated on the Dauki fault. 

Professor Maksud Kamal stated that the Dauki fault is an active fault line, and its activity has been observed for a considerable duration. Bangladesh is situated at its southeastern end, while India's Meghalaya and Assam are in the west.

It has been noted that significant earthquakes have historically occurred at the western end of this fault. The calculated interval of 300 years between two major earthquakes is based on the occurrences at the western end.

However, no major earthquakes have been recorded in this fault since 1950, when an earthquake with a magnitude of 8.6 on the Richter scale took place. 

Maksud Kamal emphasised that the risk of a major earthquake in the southeastern part of Bangladesh or the nearby areas along the Dauki fault cannot be ruled out.