Earthquakes in NE are attributed to tectonic sources in Himalayas: NCS

Staff Reporter

GUWAHATI: The occurrence of earthquakes in the northeastern region is attributed mainly to the tectonic sources in the Himalaya, such as the Himalayan Frontal Thrust (HFT), Main Boundary Thrust (MBT), Main Central Thrust (MCT), Kopili Fault, and Dhubri Fault. The National Centre for Seismology (NCS) under the Ministry of Earth Sciences said this in a report issued close on the heels of the 5.9 magnitude earthquake that jolted Assam and its neighboring states in the wee hours of January 5.

The earthquake that jolted Assam is the first tremor in the state this year. In November 2025, a total of 53 earthquakes occurred within the Indian territory, including nine in Assam. This was the highest number of earthquakes in a state among all states in the country. The Northeast recorded 25 earthquakes in November 2025, which is the highest among regions in India.

In its report, the NCS said that a moderate earthquake of magnitude 5.1 occurred in Morigaon district, Assam, on January 5, 2026, at 04:17:40 IST with the epicenter at 26.37° N and 92.29° E at a focal depth of 50 km. The epicentre is in the Morigaon region, which is 65 km NE of Guwahati, 141 km SE of Tawang, 185 km NW of Silchar, 230 km NE of Tura, and 290 km SW of Dibrugarh.

The preliminary analysis shows that the events are located near the Kopili Fault and closer to the September 14, 2025, M 5.1 Udalguri earthquake.

The preliminary fault plane solution derived from moment tensor inversion suggests that the earthquake is associated with a thrust fault mechanism, the NCS said.

According to NCS, the felt report of maximum intensity IV (MMI scale) and minimum intensity of II have been reported from a distance around 5 km and 500 km from the epicentre respectively. No aftershocks have been reported till the preparation of the report. However, the seismic shaking gets attenuated at the fastest pace because the source zones of the main shock are already associated with fractures and cracks since the April 2021 Sonitpur EQ (M 6.4) and its subsequent aftershock sequence.

The historical and instrumentally recorded earthquake data (NCS catalogue) reveals that the region is affected by moderate to large earthquakes. The most prominent events among these are the M 6.4 on April 28, 2021; the M 6.4 on Sept 21, 2009, Bhutan earthquake; and the July 29, 1960, Assam earthquake of M 6.0.

In addition to the above, noteworthy earthquakes and the events originating in Assam and the neighbouring region are often felt in the region with slight to strong intensity. The occurrence of earthquakes in the region is attributed mainly to the tectonic sources in the Himalaya, such as the Himalayan Frontal Thrust (HFT), Main Boundary Thrust (MBT), Main Central Thrust (MCT), Kopili Fault, and Dhubari Fault. Seismologically, as well as geologically, it is evidenced that the region has been quite active and falls in the highest seismic hazard zone, V. The Assam region falls in the high seismic zone VI (2025) of the seismic zoning map of the Bureau of Indian Standards (BIS). 

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