India’s Updated Seismic Zonation Map (2025)

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  • This revision aims to align India’s seismic safety standards with modern scientific understanding, replacing the outdated 2016 map and historical-epicentre-based models.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• Outdated Methodology: Older models relied heavily on known past earthquake locations, magnitudes, broad geology, soil types & historical damage patterns.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