Syllabus: GS-III & V: Natural Disaster

Why in the News?

• Recently, a magnitude 5.8 earthquake struck Udalguri district in Assam at a shallow depth of about 5 km.
  

More About the News

• Tremors were strongly felt in Guwahati and other districts of Assam, as well as in Arunachal Pradesh, West Bengal, and Bhutan.
  
• Although no fatalities occurred, two children sustained injuries in a wall collapse and minor cracks were reported in buildings across several districts.
  
• The event has renewed urgent debates on Assam’s vulnerability to earthquakes and the state’s preparedness for a future mega quake.
  

Assam’s Seismic Profile: A Tectonic Hotspot

• Assam is located in Seismic Zone V, the highest risk category in India’s seismic zoning map.
  
• The state lies at the collision junction of two major tectonic systems:
  
  • Eastern Himalayas to the north.
    
  • Indo-Burmese subduction zone to the east.
    
• The Indian plate pushes against the Eurasian plate at a rate of 4–5 cm annually, generating immense stress.
  
• Probabilistic Seismic Hazard Assessments (PSHA) for Northeast India estimate Peak Ground Acceleration (PGA) values ranging from 0.16g to 0.57g, and in some areas up to 0.77g — strong enough to cause severe shaking and widespread damage.
  

Historical Context: Lessons from the Past

• 1897 Shillong Earthquake: Magnitude 8.1, caused catastrophic damage across Assam, collapsing buildings and reshaping landscapes.
  
• 1950 Assam–Tibet Earthquake: Magnitude 8.6, among the largest in recorded history, triggered massive landslides, floods, and permanent changes in the Brahmaputra’s course.
  
• 2012 Assam Earthquake: Magnitude 6.4, caused relatively minor damage due to the release of stress through smaller preceding quakes.
  
• 2021 Sonitpur Earthquake: Magnitude 6.0, highlighted vulnerabilities in rural and semi-urban construction, where non-engineered masonry structures suffered the most.

These events confirm that large-magnitude quakes are a recurring reality in Assam and the seismic gap since 1950 increases future risk.

The “Assam Seismic Gap”

• Since the 1950 mega quake, Assam has not experienced another great earthquake, creating a seismic gap of over 70 years.
  
• Scientific studies suggest that this dormant phase indicates massive stress accumulation.
  
• Optically Stimulated Luminescence (OSL) dating indicates that such events recur approximately every 480 years, but smaller quakes do not rule out the possibility of an earlier rupture.
  

Experts warn that this seismic gap makes Assam a potential site for a future large-magnitude earthquake.

Scientific Insights and Current Research

Advances in Seismology

• According to Dr. O.P. Mishra, Director of the National Centre for Seismology (NCS):
  
  • India has advanced through three stages of earthquake research — mapping fault lines, identifying earthquake-prone zones, and conducting microzonation of cities.
    
  • The fourth stage — precise prediction of time, place, and magnitude — remains beyond current scientific ability.
    
  • Collaborative research with Japan, China, Taiwan, Russia, and Greece is ongoing, but no breakthrough has yet occurred.
    

On Animal Behaviour

• Some countries experimented with observing reptiles, birds, and mammals for abnormal behaviour before quakes.
  
• Example: Cobras emerging from holes before a quake — but this was later found to happen due to unrelated factors as well.
  
• Conclusion: Animal behaviour is not a reliable predictor.
  

Role of Small Earthquakes

• Dr. Mishra clarified that frequent small tremors are not necessarily precursors of a mega quake.
  
• Instead, they can be positive, as they gradually release accumulated stress.
  
• Example: The 2012 quake (M 6.4) and the 2025 quake (M 5.8) caused limited damage because smaller tremors in prior years had dissipated some seismic energy.
  

Present Concerns

1. Urbanisation Risks
   
   • Guwahati and other growing cities face unplanned construction, poor compliance with building codes, and rising population density.
     
   • Skyscrapers, flyovers, and commercial hubs add to seismic exposure.
     
2. Infrastructure Fragility
   
   • Vital assets like Brahmaputra bridges, mega power projects, ethanol plants, and refineries are vulnerable.
     
   • A large quake could cause massive economic losses and disrupt connectivity.
     
3. Environmental Impact
   
   • Earthquakes in Assam could trigger landslides, floods, and erosion, worsening existing ecological challenges.
     
   • Riverbank erosion along the Brahmaputra would magnify displacement and poverty.
     
4. Socio-Economic Risks
   
   • Millions of rural households depend on fragile housing and agriculture.
     
   • A mega quake could lead to mass displacement, loss of livelihoods, and psychological trauma.
     

 Challenges in Seismology

1. Prediction Limitations

• Exact time, location, and magnitude of earthquakes cannot be predicted with current science.
  
• Only hazard zoning and fault-line mapping are possible.
  
• Final-stage prediction (epicentre + timing) remains out of reach.
  

2. Complex Geological Settings

• Regions like Northeast India sit at multi-plate collision zones (Indian, Eurasian, Burmese plates).
  
• Highly heterogeneous geology makes modelling difficult.
  

3. Data Limitations

• Sparse seismic monitoring networks in developing countries.
  
• Lack of real-time data sharing across borders (e.g., Indo-China region).
  
• Incomplete historical earthquake records.
  

4. Technological Gaps

• Early warning systems are expensive and technologically demanding.
  
• India is still building capacity compared to Japan or Taiwan.
  
• High reliance on imported equipment.
  

5. Socio-Economic Challenges

• Weak enforcement of building codes → unsafe infrastructure.
  
• High costs of retrofitting old buildings.
  
• Resistance in rural/semi-urban areas to adopting quake-resilient designs.
  

6. Animal Behaviour & Alternative Theories

• No conclusive evidence that animal behaviour can predict quakes.
  
• False positives make such theories unreliable.
  

7. Seismic Gap Uncertainty

• Long dormant periods (like Assam since 1950) create prediction dilemmas:
  
  • Does stress build-up mean a big quake is imminent?
    
  • Or are small tremors enough to release pressure?
    
• Science has no clear answers.
  

8. Public Awareness & Preparedness

• Communities often lack awareness of earthquake risks.
  
• Preparedness drills are irregular.
  
• Myths and misinformation reduce trust in scientific warnings.
  

9. Institutional & Policy Challenges

• Disaster management agencies lack funds, manpower, and coordination.
  
• Seismological research needs more interdisciplinary collaboration (geology, engineering, AI).

Way Forward

1. Strengthening Infrastructure

• Enforce Bureau of Indian Standards (BIS) earthquake codes in all new construction.
  
• Retrofitting of old buildings, especially schools, hospitals, and government offices.
  
• Promote indigenous earthquake-resistant materials like bamboo composites.
  

2. Scientific and Technological Measures

• Expand seismic microzonation to all major cities of Assam and the Northeast.
  
• Invest in AI-driven early warning systems for urban centres.
  
• Build collaborations with Japan and Taiwan to replicate their resilient building practices.
  

3. Community Preparedness

• Conduct regular mock drills and public awareness campaigns.
  
• Introduce earthquake education in schools and universities.
  
• Establish local self-help groups for quick first response in villages and towns.
  

4. Institutional Strengthening

• Empower the Assam State Disaster Management Authority (ASDMA) with funds and trained manpower.
  
• Ensure coordination with NDMA, IMD, NESAC, and armed forces for multi-level response.
  

5. Integrating Resilience with Development

• Ensure all major infrastructure projects like bridges, refineries, and power plants include earthquake-resilient designs.
  
• Promote flood- and quake-resilient housing in erosion-prone rural areas.
  
• Tie disaster preparedness with sustainable economic growth.
  

Conclusion

Assam’s seismic vulnerability is an inescapable reality, rooted in its geology and tectonic position. While science has made progress in identifying fault lines and vulnerable zones, exact prediction of earthquakes remains impossible. The September 2025 quake serves as a wake-up call — showing both the dangers of complacency and the benefits of stress-releasing smaller tremors.

The path forward lies in a holistic resilience strategy: strict building norms, retrofitting of old infrastructure, scientific innovation, community-level awareness, and integration of disaster management into developmental planning. If implemented effectively, Assam can transform this challenge into an opportunity for sustainable, disaster-resilient growth.

1. Assam is considered one of the most earthquake-prone regions of the world. Discuss the factors contributing to its vulnerability and suggest a multi-pronged strategy to mitigate the risks. (150 Words/10 marks)