Frequent earthquakes release the energy and prevent a mega quake. (Representational image)
An earthquake of magnitude 5.8 struck the Udalguri district of Assam on September 14, causing damage to properties across several districts.
There were reports of cracks in walls and ceilings, while the jolt was also said to have triggered landslides in Guwahati and Lumding. In one incident, three hostel students were injured when a ceiling collapsed in Udalguri. The tremor was strongly felt due to the shallow depth of the epicentre – only 5 km below the surface.
Seismological analysis revealed that the mainshock and subsequent aftershocks were located near the Kopili Fault, close to the epicentre of the April 28, 2021, Sonitpur quake, which measured 6.4 on the Richter scale. The recent quake’s effects were felt up to 500 km from the epicentre. The Kopili Fault is among the most seismically active faults in the Northeast.
Historically, it was the source of the 1942 earthquake (magnitude 7) and the devastating 1869 Cachar quake (magnitude 7.5). Earthquakes of magnitude 4-5 are frequent in this region, which lies in Seismic Zone V – the highest risk category as per the Bureau of Indian Standards (BIS) seismic zoning map.
The high seismicity in Assam and its neighbouring regions is primarily attributed to tectonic features such as the Himalayan Frontal Thrust (HFT), Main Boundary Thrust (MBT), Main Central Thrust (MCT), Kopili Fault, and Dhubri Fault. These geotectonic structures contribute to frequent and often damaging seismic activity in the region.
To reduce casualties and damage from future quakes, especially in such high-risk areas, awareness and strict adherence to earthquake-resistant construction practices are essential. All buildings, especially high-rise and engineering structures, should be designed using microzonation maps, which help identify local ground conditions and seismic amplification zones.
These maps ensure that the predominant frequency of ground motion does not coincide with a building’s natural frequency, thereby minimising the risk of structural collapse. Countries like Japan, New Zealand, and even developing nations like Mexico have successfully reduced quake-related casualties by rigorously implementing microzonation-based planning and construction standards. In India, the National Centre for Seismology has initiated microzonation projects for around 80 cities, with several already completed.
The microzonation map for Guwahati, for instance, was prepared in 2005-07, but it remains unclear whether these guidelines are actively followed for building approvals and construction in the city. While scientific institutions can provide vital data and tools like microzonation maps, it is the responsibility of administrative and regulatory authorities to ensure their implementation. Without strict enforcement of building codes and seismic planning regulations, the region will remain vulnerable to avoidable damage and loss of life in future tremors. Proactive planning today is the only way to secure a safer tomorrow.