India has released a revised seismic zonation map under the updated Earthquake Design Code by the Bureau of Indian Standards (BIS). For the first time, the entire Himalayan arc has been placed in the newly introduced highest-risk Zone VI, marking a major update in the country’s earthquake hazard assessment.

The new map shows that 61% of India now falls under moderate to high seismic hazard zones, a significant rise from previous estimates.

Earlier, the Himalayan region was split across Zones IV and V, which underestimated the danger from long-unruptured fault segments, particularly in the central Himalayas. Some of these areas have not experienced a major earthquake for nearly 200 years.

The Himalayas are highly vulnerable because the Indian Plate continuously pushes northward into the Eurasian Plate at about five centimetres per year, creating enormous stress beneath the Earth’s crust. This tectonic activity, combined with the young and still-adjusting geology of the region, makes it prone to powerful earthquakes.

Major fault lines, including the Main Frontal Thrust, Main Boundary Thrust, and Main Central Thrust, run beneath the Himalayas. Scientists have identified long seismic gaps, indicating that large earthquakes may be due to stored energy in these faults.

The revised map incorporates rupture propagation southward along the Himalayan Frontal Thrust, extending risks to areas such as Dehradun near Mohand.

Other changes include:

  • Reclassifying the outer Himalaya, where faults could trigger quakes affecting populated foothills.

  • Assigning higher-risk zones to boundary towns, prioritising geological realities over administrative divisions.

These updates are intended to guide engineers and urban planners to adopt stricter safety standards for buildings, bridges, and other infrastructure in vulnerable areas.

The map highlights seismic risks for densely populated states like Uttarakhand, Himachal Pradesh, and parts of Uttar Pradesh. Authorities now recommend retrofitting existing infrastructure and avoiding construction on soft sediments or active faults.

Experts have welcomed the update, saying the uniform classification improves disaster preparedness amid increasing urbanisation and development.

This overhaul, developed through advanced modelling, is expected to reshape building codes, disaster planning, and urban development across India, helping the country become more resilient to earthquakes in the future.