After the first massive earthquake measuring 6.4 Magnitude on the Richter scale hit Assam and parts of Northeast early Wednesday, so far as of 1:30 PM on Thursday, twenty aftershocks have been reported by the National Centre of Seismology (NCS), Government of India. Eighteen from Sonitpur and one each from Nagaon and Morigaon district.
The total tremors felt in Assam in the last 24-hours stands at 21. The most recent one took place on the afternoon of April 29. All the tremors have the epicenter in and around Dhekiajuli in the Sonitpur district of Assam.
The high magnitude earthquake and the frequent aftershocks have done considerable damage to properties all over the region. This has also caused huge panic among the people of Assam. Many people have left their high-rise apartments in fear of further tremors.
Headline8 spoke to one such person, Mriganka Pathak, and he said, “My apartment was greatly damaged by the huge earthquake that took place yesterday. Cracks have appeared at various parts of my apartment. My apartment is more than 20 years old and I fear that another strong tremor might result in a disaster. I am scared for my life and that is why I have shifted to my friend’s place for the next few days.”
So, what has led to the tremors in the region?
The tremors have been attributed by the NCS to the Kopili fault zone closer to Himalayan Frontal Thrust. This is a seismically active area falling in the highest Seismic Hazard Zone V. The main cause of this high seismicity is its unique placement of tectonic plates and their interactions. It is associated with collisional tectonics because of the Indian Plate subducting beneath the Eurasian Plate. Subduction is a geological process in which one crustal plate is forced below the edge of another.
The Kopili Fault is known to be a 300-kilometer northwest-southeast trending fault from the western part of Manipur up to the tri-junction of Bhutan, Arunachal Pradesh and Assam. The fault itself is a transpressional fracture that generates lower crustal dextral strike-slip earthquakes.
According to Prof Chandan Mahanta of the Department of Civil Engineering at IIT-Guwahati, the earthquake took place because of accumulated stress release. At this epicentre, stress was probably constrained for a fairly long time; hence there was relatively higher intensity release.
In addition, scientist Nilutpal Bora who is currently a postdoctoral fellow in the Department of Civil Engineering at IIT-Guwahati, on Wednesday said, “There was a gap of 74 years between the two major earthquakes of 1869 and 1943. Multiple studies opined a major earthquake event around 2017 to repeat this cycle… Recent seismicity discovered along the Kopili fault led to speculations that this fault is one of the most seismically active faults of the region and a major earthquake could be expected in the future, which has somehow been validated by today’s event.”