Syllabus: GS– I & V: Physical Geography

Why in the news?

Two back to back moderate earthquakes of magnitude 5.1 struck Assam in the early hours of January 5, 2026, with its epicentre in Morigaon district. Soon after, the National Centre for Seismology (NCS) under the Ministry of Earth Sciences released a detailed analysis attributing earthquakes in the Northeast mainly to active tectonic sources associated with the Himalayas, such as major thrusts and regional faults. The event once again highlighted the region’s extreme seismic vulnerability.

Seismic setting of Northeast India

Northeast India lies at the junction of the Indian Plate, Eurasian Plate, and Burma Plate, making it one of the most tectonically complex and earthquake-prone regions in the world.

• The Indian Plate is moving northwards and colliding with the Eurasian Plate, leading to crustal compression and faulting.
  
• Simultaneously, interaction with the Indo-Burma subduction zone adds further tectonic stress.
  
• This convergence explains why earthquakes here are frequent, shallow to intermediate in depth, and sometimes destructive.
  

Major tectonic sources behind earthquakes

The NCS report identifies several active tectonic structures responsible for seismicity:

• Himalayan Frontal Thrust – The southernmost and youngest thrust of the Himalayas, marking active crustal shortening.
  
• Main Boundary Thrust – Separates the outer and lesser Himalayas and is a major earthquake-generating structure.
  
• Main Central Thrust – A deep-seated thrust accommodating large-scale plate convergence.
  
• Kopili Fault – A prominent strike-slip fault running across Assam, frequently linked with moderate earthquakes.
  
• Dhubri Fault – Another regional fault contributing to seismic instability in western Assam.
  

These faults release accumulated tectonic stress through thrust and strike-slip fault mechanisms, as seen in the January 2026 event.

Recent and historical earthquake pattern

• Assam recorded nine earthquakes in November 2025, the highest among Indian states.
  
• The Northeast region experienced 25 earthquakes in the same month, the highest for any region.
  
• Significant past earthquakes include:
  
  • 1950 Assam earthquake (magnitude 8.6) – one of the strongest in recorded history.
    
  • 1960 Assam earthquake (magnitude 6.0).
    
  • 2009 Bhutan earthquake (magnitude 6.4).
    
  • 2021 Sonitpur earthquake (magnitude 6.4).
    

These events confirm that the region is affected by moderate to large earthquakes at regular intervals.

Seismic hazard zoning

• The Bureau of Indian Standards places much of Northeast India in Seismic Zone V, the highest hazard category.
  
• Assam is classified under very high seismic risk, meaning even moderate earthquakes can cause damage due to:
  
  • Soft alluvial soils of the Brahmaputra valley.
    
  • High population density in urban centres.
    
  • Non-earthquake-resistant construction.
    

Why damage risk remains high

• Shallow focus earthquakes transmit stronger surface shaking.
  
• Liquefaction-prone sediments amplify damage in riverine areas.
  
• Rapid urbanisation without strict adherence to seismic building codes.
  
• Limited public awareness and preparedness.
  

Government initiatives and institutional response

• National Centre for Seismology operates a nationwide seismic monitoring network and issues rapid assessments.
  
• Satellite-based and instrument-based monitoring helps in real-time detection.
  
• Disaster Management Authorities at national and state levels conduct preparedness and response planning.
  
• Bureau of Indian Standards seismic codes prescribe earthquake-resistant construction norms.
  

Way forward

• Strict enforcement of earthquake-resistant building codes, especially in Zone V areas.
  
• Microzonation studies for cities like Guwahati to identify local risk variations.
  
• Public awareness and mock drills to reduce panic and casualties.
  
• Integration of disaster risk reduction into urban planning and infrastructure projects.
  
• Strengthening early warning, monitoring, and rapid response systems.
  

Conclusion

Earthquakes in Northeast India are not random events but the result of active Himalayan tectonics and regional fault systems. Scientific evidence clearly shows that the region will continue to experience seismic activity. The challenge, therefore, is not prevention, but preparedness, resilience, and risk-informed development.

Exam Hook – Mains

Key Takeaway: Northeast India’s high seismicity is driven by Himalayan thrusts and regional faults, making disaster preparedness and resilient infrastructure essential.

Probable Question:
“Explain the tectonic causes of frequent earthquakes in Northeast India and discuss measures needed to reduce seismic risk in the region.”

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