India has unveiled a groundbreaking seismic zonation map that fundamentally reshapes the country's understanding of earthquake risks. The newly released Earthquake Design Code places the entire Himalayan arc in the newly introduced highest-risk Zone VI for the first time, marking a significant shift in how India approaches earthquake preparedness.
Redefining India's Seismic Landscape
The updated map reveals that 61% of India now falls within moderate to high hazard zones, a substantial increase that demands immediate attention from urban planners, engineers, and policymakers. This revision represents one of the most significant changes in India's seismic hazard assessment in decades, fundamentally altering how buildings, infrastructure, and urban expansion must respond to persistent tectonic stresses beneath some of the most densely populated regions.
Vineet Gahalaut, director of the Wadia Institute of Himalayan Geology and former director of the National Centre for Seismology, emphasized that the updated map finally brings much-needed uniformity to the Himalayan belt. "The earlier zonation did not fully account for the behaviour of these locked segments, which continue to accumulate stress," he explained, noting that previous versions underestimated risks posed by long-unruptured fault segments.
Scientific Advancements Behind the New Mapping
The Bureau of Indian Standards (BIS), which released the updated zonation as part of the revised Earthquake Design Code, built the new map using internationally accepted probabilistic seismic hazard assessment (PSHA) methods. This sophisticated approach incorporates detailed data on:
- Active faults and their maximum potential magnitude
- Ground shaking patterns with distance
- Regional tectonic regimes
- Lithology underlying various terrains
This methodology replaces the earlier approach that relied heavily on known epicenters and magnitudes of past earthquakes, broad geological features, and historical damage surveys. The new system provides a clearer understanding of peak ground accelerations expected during future earthquakes.
Enhanced Safety Requirements for Buildings
The revised design code introduces sweeping safety requirements for both structural and non-structural elements. For the first time, non-structural components such as parapets, ceilings, overhead tanks, façade panels, electrical lines, lifts, and suspended fixtures receive focused attention.
Under the new norms, all heavy non-structural components exceeding 1% of a building's total weight must be securely anchored and braced to prevent internal collapses that endanger occupants. Engineers confirm this requirement will significantly reduce avoidable injuries during moderate earthquakes.
For buildings located near active faults, the code mandates that structural design must consider severe pulse-like ground motions characteristic of near-fault earthquakes. It introduces updated limits relating to displacement, ductility, and energy dissipation to prevent catastrophic failures.
Critical Infrastructure and Urban Planning Implications
The updated norms tighten performance expectations for critical infrastructure including hospitals, schools, bridges, pipelines, and major public buildings. These facilities must remain functional after a major earthquake to support emergency response and continuity of essential services.
Another major addition to the 2025 map is the introduction of an "exposure window" that accounts for population density, infrastructure concentration, and socioeconomic vulnerability using the probabilistic exposure and multi-hazard assessment (PEMA) method. This ensures seismic zoning captures not just physical hazard but also potential impact on communities, particularly in urbanizing regions where even moderate shaking can trigger widespread disruption.
The BIS has urged that all new structures and infrastructure projects immediately adopt the 2025 version instead of the 2016 map, ensuring safety standards reflect the current assessment of seismic activity. This shift assumes critical importance as nearly three-fourths of India's population now lives in seismically active areas.
