Assam quake linked to Kopili Fault; no aftershocks recorded: NCS

Guwahati: A 5.1-magnitude earthquake that struck central Assam in the early hours of January 5 has been linked to tectonic activity near the Kopili Fault, the National Centre for Seismology (NCS) said in its preliminary assessment.

The tremor occurred at 4:17:40 am. Its epicentre lay in Morigaon district at a depth of 50 km, around 65 km northeast of Guwahati. The quake was felt across large parts of Assam and adjoining states, the NCS report noted.

According to seismologists, the earthquake was associated with a thrust fault mechanism. It occurred close to the zone that experienced a 5.1-magnitude quake in Udalguri in September 2025, pointing to sustained tectonic activity along the corridor.

The shaking registered Modified Mercalli Intensity (MMI) levels between II and IV. Noticeable tremors were felt within a radius of nearly 200 km from the epicentre. The NCS received 90 felt reports through its website and the BhooKamp mobile app, indicating light to moderate ground shaking.

Notably, no aftershocks were recorded until the report was prepared. Scientists said the seismic energy may have dissipated rapidly, as the source zone has already been weakened by earlier major events, including the April 2021 Sonitpur earthquake (M 6.4) and its subsequent aftershocks.

The report reiterated that Assam lies in one of India’s most seismically active regions. The state’s seismicity is shaped by major tectonic structures such as the Himalayan Frontal Thrust, Main Boundary Thrust, Main Central Thrust, Kopili Fault, and Dhubri Fault.

According to the Bureau of Indian Standards’ seismic zoning map (2025), Assam falls within high seismic hazard zones.

Authorities have advised continued vigilance. However, no major structural damage was reported following the January 5 tremor.