India's Revised Seismic Zonation Map

A significant update has been made to India's national seismic zonation map under the revised Earthquake Design Code, with the entire Himalayan arc now classified as the highest-risk Zone VI for the first time.

Key Updates

• 61% of India is now categorized under moderate to high seismic hazard zones.
• The map enhances how buildings and infrastructure will be constructed in earthquake-prone areas.
• New map provides uniformity across the Himalayan belt, previously split across Zones IV and V.
• Recognizes the risks of long-unruptured fault segments, particularly in the central Himalayas.

Scientific and Data-Driven Approach

• Adopts internationally accepted probabilistic seismic hazard assessment (PSHA) methods.
• Incorporates data on active faults, maximum potential magnitudes, and tectonic regimes.
• Shifts away from reliance on past epicentres and broad soil features of earlier maps.

Updated Construction Code

• Infrastructure projects urged to adopt the new 2025 code.
• Introduces safety requirements for structural and non-structural components.
• Mandatory secure anchoring for elements like parapets, ceilings, and façades.
• Designs near active faults must withstand severe pulse-like ground motions.

New Safety Norms

• New norms cover liquefaction, soil flexibility, and site-specific ground-response spectra.
• Critical infrastructure must remain functional post-earthquake to ensure emergency response and service continuity.

Exposure Window and Socioeconomic Considerations

• Introduction of an "exposure window" that considers population density and infrastructure concentration.
• Ensures zoning reflects both geological hazard and community-level impact.

Regional Impact

• Significant changes in the Himalayan region, minor refinements in the stable southern peninsula.