India Revised Earthquake Design Code, 2025

Source: ET

Subject: Geography

Context: India has released a radically updated seismic zonation map under the revised Earthquake Design Code (2025), placing the entire Himalayan arc in a newly created highest-risk Zone VI for the first time.

About India Revised Earthquake Design Code, 2025:

What is the Seismic Zonation Map?

• A seismic zonation map classifies different regions of India based on their earthquake hazard potential, helping determine how strong structures must be to withstand earthquakes.

Published by:

• The updated map is issued by the Bureau of Indian Standards (BIS) as part of the revised Earthquake Design Code, 2025 (IS 1893).

• It uses internationally accepted Probabilistic Seismic Hazard Assessment (PSHA)

Key Features of the Revised Zonation Map:

• Introduction of Highest-Risk Zone VI:

• Entire Himalayan arc (J&K–Ladakh to Arunachal) placed in Zone VI, the most hazardous zone, for the first time. Recognises consistent, extreme tectonic stress along the Indian–Eurasian plate boundary.

• Entire Himalayan arc (J&K–Ladakh to Arunachal) placed in Zone VI, the most hazardous zone, for the first time.

• Recognises consistent, extreme tectonic stress along the Indian–Eurasian plate boundary.

• 61% of India Now in Moderate to High Hazard Zones:

• A major jump from older estimates relying mainly on past epicentres. Reflects scientific modelling of fault segments, locked sections, and rupture potential.

• A major jump from older estimates relying mainly on past epicentres.

• Reflects scientific modelling of fault segments, locked sections, and rupture potential.

• Boundary Towns Auto-Upgraded to Higher-Risk Zone:

• If a city lies on the border of two zones, it defaults to the higher-risk one. Moves away from administrative lines to geological realities.

• If a city lies on the border of two zones, it defaults to the higher-risk one.

• Moves away from administrative lines to geological realities.

• Inclusion of Rupture Propagation Southward:

• Acknowledges that Himalayan Frontal Thrust ruptures may extend south to populated foothill regions like Dehradun (near Mohand).

• Mandatory Structural & Non-Structural Safety:

• New norms for anchoring parapets, ceilings, tanks, façades, HVAC units, etc., if their weight exceeds 1% of total load. Buildings near active faults must withstand pulse-like ground motions typical of near-fault quakes.

• New norms for anchoring parapets, ceilings, tanks, façades, HVAC units, etc., if their weight exceeds 1% of total load.

• Buildings near active faults must withstand pulse-like ground motions typical of near-fault quakes.

• New Soil & Ground-Response Requirements:

• Detailed provisions for liquefaction, soil flexibility, site-specific shaking spectra. Encourages geotechnical investigations before major construction.

• Detailed provisions for liquefaction, soil flexibility, site-specific shaking spectra.

• Encourages geotechnical investigations before major construction.

• Exposure Mapping (PEMA Method):

• Incorporates population density, infrastructure concentration and socioeconomic vulnerability. Integrates impact-based assessment with geological hazard.

• Incorporates population density, infrastructure concentration and socioeconomic vulnerability.

• Integrates impact-based assessment with geological hazard.

Significance:

• Improved Earthquake Preparedness: Accurate hazard modelling ensures stronger building codes for at-risk regions, especially the Himalayas.

• Retrofitting Imperative: Old structures, especially in Himalayan towns, must be retrofitted, including schools, hospitals, and bridges.

• Uniformity Across the Himalayan Arc: Fixes decades of underestimation due to inconsistent older maps (Zones IV & V), despite identical tectonics.