This earthquake increased risk for Bangladesh, says expert

Yesterday, Friday, Myanmar experienced two consecutive earthquakes. The first had a magnitude of 7.7, followed by another earthquake just 12 minutes later, measuring 6.4 in magnitude. The epicentre of the powerful earthquake was near the city of Sagaing in Mandalay, Myanmar.

Sagaing is situated along an extensive fault line that stretches 1,200 kilometres from Arunachal Pradesh in India to the Andaman Sea. Over the past 185 years, this fault has experienced more than seven major earthquakes, the largest of which occurred in 1839 with a magnitude of 8.3.

The recent earthquake caused significant damage more than 1,000 kilometres away in Bangkok, where high-rise buildings and numerous roads were severely affected. Myanmar itself suffered extensive destruction. The earthquake was also felt in parts of China and Bihar, India. This earthquake occurred within the Indo-Burma subduction zone.

A subduction zone is a region where two tectonic plates collide, causing one plate to be forced beneath the other. The Indo-Burma subduction zone extended as far as the south-eastern region of Bangladesh and it’s recognised as an earthquake-prone area.

This Indo-Burma subduction zone is further divided into several sections, including a locked zone and a slow-slip zone. Dangerous earthquakes occur in locked zone and are located at the eastern edge of Bangladesh, towards the western part of the subduction zone.

In addition to these two sub-zones, the Sagaing Fault is also situated within the Indo-Burma subduction zone. This fault lies at the junction of the Shan Plateau and the Central Myanmar Basin, where the recent earthquake originated.

The region is earthquake-prone but possesses some distinct geological characteristics. Previously, in 1930, a 7.4 magnitude earthquake struck Bago, an area situated near the sea. At that time, the earthquake also triggered a tsunami.

From the very beginning, we have maintained that there are two primary sources of earthquakes affecting our region. One is the Indo-Burma subduction zone, located to the east of Bangladesh, while the other is the Dauki Fault and the Himalayan foothill region to the north.

Among these, the subduction zone poses the greatest risk. The locked area of this subduction zone extends from the Sunamganj-Kishoreganj-Meghna River region in Bangladesh to the Manipur-Mizoram region in India. Here, the two tectonic plates are interlocked. The Indian Plate lies beneath, while the Burma Plate is positioned above. This interlocking occurs due to high levels of frictional energy.

To explain this in simpler terms, if you rub a surface covered in oil, it will slip easily; however, if you rub two pieces of sandpaper together, they will resist movement and remain stuck. The locked zone in our region experiences significantly high frictional force, which is why earthquakes occur less frequently.

However, this makes the situation even more hazardous. Why is this dangerous? Because a major earthquake occurred in this region between 800 and 1,000 years ago, releasing a significant amount of stored energy. Since then, new energy has been accumulating and the region now holds the potential for an earthquake of magnitude 8.2 to 9.

The earthquake that occurred yesterday is unrelated to this stored energy. Although it took place within the subduction zone, it was outside our immediate area. However, if one assumes that a large earthquake in the subduction zone has now reduced our risk that would be incorrect. On the contrary, the situation has become even more precarious, as our earthquake-prone zone has now had the opportunity to accumulate more energy, increasing the potential threat. 

We must therefore remain prepared. This requires short-term, medium-term and long-term planning. There is no alternative to raising widespread public awareness. People must be properly trained and it is essential to establish a system for conducting regular drills.

* Humayun Akhter, earthquake researcher and former professor at the Department of Geology in Dhaka University.