India has unveiled a radically updated seismic zonation map under the updated Earthquake Design Code, placing the entire Himalayan arc in a newly created Zone VI, the highest-risk category introduced for the first time, according to a report in The Times of India.
The new map significantly reshapes India’s assessment of earthquake exposure, revealing that 61% of the country now falls under moderate to high hazard zones, the report said.
The latest map is likely to influence future building norms, infrastructure planning and urban development.
Vineet Gahalaut, director of the Wadia Institute of Himalayan Geology and former head of the National Centre for Seismology, said the update finally brings long-needed consistency to the Himalayan belt, which was previously split between Zones IV and V despite sharing uniform tectonic stress, the TOI report said.
He noted that earlier versions underestimated the threat from long-unruptured fault segments.
The revision marks one of the most significant overhauls of India’s seismic risk assessment in decades. Scientists say the fresh mapping now recognises the likelihood of ruptures in the outer Himalayas propagating southward until they meet the Himalayan Frontal Thrust, which in the Dehradun region begins near Mohand.
Senior experts also told TOI that the update removes abrupt hazard changes that once existed simply because of administrative boundaries.
A key rule introduced in the new map places any town located on the boundary between two zones automatically into the higher-risk category. Officials said this ensures planners no longer rely on outdated assumptions about local hazard conditions.
The Bureau of Indian Standards (BIS), which released the updated zonation, said the map is based on probabilistic seismic hazard assessment (PSHA) methods that incorporate detailed information on active faults, maximum potential magnitudes, attenuation of seismic waves, tectonic regimes and underlying lithology, the report said. This replaces the earlier approach that relied heavily on historical epicentres, broad geological groupings and past damage reports.
BIS has urged that all new construction adopt the 2025 edition of the code so that safety standards reflect current scientific understanding. The shift comes as nearly three-fourths of India’s population now lives in seismically active areas.
The revised design code introduces comprehensive safety requirements for both structural and non-structural components. For the first time, heavy non-structural elements exceeding 1% of a building’s weight must be anchored to prevent internal collapses that often cause injuries in moderate earthquakes.
For projects near active faults, the code mandates design provisions that account for strong pulse-like ground motions. Updated limits on displacement, ductility and energy dissipation aim to reduce the risk of catastrophic structural failures.
Critical infrastructure — including hospitals, schools, bridges and pipelines — must now remain functional after major earthquakes, aligning India’s standards with global resilience-focused practices, it said.
The new map also incorporates an “exposure window” that reflects population density, infrastructure concentration and socioeconomic vulnerability, ensuring that seismic zoning captures both physical hazard and potential community impact.
While the Himalayas saw sweeping revisions, the southern peninsula experienced only minor refinements, with its overall hazard profile remaining largely unchanged due to its relatively stable tectonic setting.
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