India’s Updated Seismic Zonation Map (2025)

Brief Context

In News India has released an updated seismic zonation map under the new Earthquake Design Code (2025). Need For Upgradation Earlier Maps Underestimated Himalayan Risk: Previous zonation divided the Himalaya into Zones IV and V, despite the belt sharing one of the world’s most active tectonic systems. Outdated Methodology: Older models relied heavily on known past earthquake locations, magnitudes, broad geology, soil types historical damage patterns.

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Syllabus: GS3/ Disaster Management

In News

• India has released an updated seismic zonation map under the new Earthquake Design Code (2025). 
  • This revision aims to align India’s seismic safety standards with modern scientific understanding, replacing the outdated 2016 map and historical-epicentre-based models.

Need For Upgradation

• Earlier Maps Underestimated Himalayan Risk: Previous zonation divided the Himalaya into Zones IV and V, despite the belt sharing one of the world’s most active tectonic systems.
• Outdated Methodology: Older models relied heavily on known past earthquake locations, magnitudes, broad geology, soil types & historical damage patterns.
• Underestimation of Rupture Propagation: Earlier maps did not adequately account for southward propagation of Himalayan Frontal Thrust ruptures
  • Populated foothill regions like Dehradun (near Mohand) faced underestimated risk despite proximity to major thrust faults.
• Growing Exposure and Vulnerability: Nearly three-fourths of India’s population now resides in seismically active areas.
• Gap with International Best Practices: Need to adopt internationally accepted Probabilistic Seismic Hazard Assessment (PSHA) methods.

What is a Seismic Zonation Map?

• A seismic zonation map is a scientific representation that divides a geographical area into zones based on the intensity and frequency of earthquakes expected in different regions.
• It is published by the Bureau of Indian Standards (BIS) & integrated into the Earthquake Design Code (IS 1893).
• It serves as a foundational tool for urban planning, risk assessment & disaster preparedness. 

Key Features of the New Seismic Map (2025)

• Introduction of Zone VI: 
  • The entire Himalayan arc (Jammu & Kashmir-Ladakh to Arunachal Pradesh) is now classified under the newly created highest-risk Zone VI.
  • Recognizes consistent, extreme tectonic stress along the Indian-Eurasian plate boundary.
• Scientific Methodology – PSHA:
  • Built using internationally accepted Probabilistic Seismic Hazard Assessment (PSHA) methods.
  • Considers ground shaking attenuation with distance, tectonic regime, and underlying lithology.
• Enhanced Geographic Coverage:
  • 61% of India’s landmass now classified under moderate to high hazard zones (increased from 59%).
  • The southern peninsula shows minor refinements with a broadly stable hazard profile due to relatively stable tectonic behavior.
• Boundary Rule Enhancement:
  • Towns situated along boundaries separating two zones will automatically be placed in the higher-risk zone.
• Comprehensive Non-Structural Elements Safety: 
  • First-time focused attention on non-structural components like parapets, ceilings, overhead tanks, façade panels, electrical lines, lifts, and suspended fixtures.

• Near-Fault Provisions:
  • Structural design must consider severe pulse-like ground motions for buildings close to active faults
  • Updated limits on displacement, ductility, and energy dissipation.
• Site-Specific Requirements: 
  • New provisions addressing liquefaction risks, soil flexibility, and site-specific response spectra.
• Critical Infrastructure Standards:
  • Hospitals, schools, bridges, pipelines, and major public buildings must remain functional after major earthquakes.

Challenges in Implementation

• Retrofitting Legacy Infrastructure: High costs of retrofitting, technical complexity & coordination challenges across multiple jurisdictions.
• Economic Burden: Higher construction costs due to stricter standards.
• Geotechnical Investigation Requirements: Site-specific assessments require specialized expertise and equipment.

Source: TOI