The Bureau of Indian Standard (BIS) has released a new earthquake zonation map of India. The entire Himalayan regime is now the highest risk Zone VI. Over 60% of India’s landmass faces moderate to high earthquake hazards.
What is India’s New Earthquake Zonation Map?
- An earthquake zonation map classifies different regions of India based on their earthquake hazard potential. It helps to determine how strong structures must be to withstand earthquakes.
- India has released a radically updated seismic zonation map under the new Earthquake Design Code (BIS, 2025). It is based on faults, maximum likely events, attenuation, tectonics, lithology, etc.
- Earlier, the Indian landmass was demarcated into four earthquake zones namely Zones II, III, IV, and V.
- Now, the updated earthquake zonation map has introduced a new highest-risk Zone VI.
- It has placed the entire Himalayan arc in this newly introduced Highest Risk Zone VI.
- Around 61% of Indian landmass now lies in moderate to high hazard zones.
- This shift will redefine how buildings, infrastructure and urban expansion must respond to the persistent tectonic stresses.
- It has brought uniformity to Himalayan belt which earlier remained split across Zones IV and V despite sharing the same underlying tectonic threat.
What are the key features of India’s New Earthquake Zonation Map?
- Under the new map, towns situated along any boundary separating two categories will now automatically be placed in the higher-risk zone VI.
- It will ensure that planners and engineers do not rely on outdated assumptions about local hazards.
- The map has been built using the internationally accepted Probabilistic Seismic Hazard Assessment (PSHA) method.
- Probabilistic Seismic Hazard Assessment (PSHA) method is a method used to estimate the likelihood of future ground shaking at a specific location.
- Moreover, this method incorporates detailed data on –
- Active faults;
- The maximum potential magnitude on each fault;
- The manner in which ground shaking diminishes with distance;
- The tectonic regime of each region, and
- The lithology underlying various terrains.
- Earlier approaches relied heavily on known epicentres, magnitudes of past earthquakes, broad geological features, soil classifications and historical damage surveys.
- However, it often led to zone adjustments around industrial townships or large cities without fully accounting for fault-specific seismic potential.
- New zonation provides clearer understanding of the peak ground accelerations that can be expected during future earthquakes.
- It urges that all new structures and infrastructure projects adopt the 2025 version instead of the 2016 map.
- The revised design code also introduces sweeping safety requirements for both structural and non-structural elements.
- It has introduced an ‘exposure window’ that accounts for population density, infrastructure concentration and socio-economic vulnerability using the Probabilistic Exposure and Multi-hazard Assessment (PEMA) method.
- The Probabilistic Exposure and Multi-hazard Assessment (PEMA) method is a recent innovation in disaster risk assessment. It integrates an “exposure window” into hazard mapping.
- It allows a comprehensive view of potential losses.
- This approach moves beyond traditional single-hazard assessments by explicitly factoring in key socio-economic exposure indicators alongside multiple potential natural hazards.
- Now onwards, it will capture not only physical hazard but also the degree of potential impact on communities, especially in urban regions. In urban regions, even moderate shaking can trigger widespread disruption due to dense construction.
India’s Earthquake Vulnerability:
- 75% of India’s population is in seismically active regions.
- 59% to 61% of landmass now under seismic risk.
- It has been 200 years since a major quake in the central Himalayas.
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Significance of the Updated Earthquake Zonation Map:
- Enhanced Earthquake Preparedness: With more precise hazard modelling, the new map supports the creation of stronger, scientifically updated building codes, especially crucial for high-risk Himalayan regions.
- Urgent Need for Retrofitting: A major takeaway is the requirement to retrofit old and vulnerable structures in Himalayan towns. This includes critical infrastructure such as schools, hospitals, government buildings, and bridges.
- Consistency Across the Himalayan Arc: The update corrects long-standing gaps and underestimations present in older maps. Despite sharing similar tectonic conditions, parts of the Himalayas were previously classified inconsistently (Zones IV & V). The new map brings uniformity and better reflects actual seismic risk.
Sources:
- https://timesofindia.indiatimes.com/city/dehradun/india-unveils-new-seismic-map-entire-himalayan-arc-now-in-highest-danger-zone/articleshow/125620899.cms
- https://www.indiatoday.in/science/story/india-unveils-new-quake-map-entire-himalayas-in-highest-risk-danger-zone-2827495-2025-11-28
FAQ:
India’s new earthquake zonation map (BIS, 2025) is an updated scientific classification of regions based on seismic hazard, introducing the highest-risk Zone VI and placing the entire Himalayan arc in it.
Zone VI was added to reflect extreme seismic risk in the Himalayan region, correcting earlier underestimations and aligning India’s standards with global scientific models.
According to the updated map, around 61% of India’s landmass falls under moderate to high seismic hazard zones, affecting both urban and rural regions.
The map is based on Probabilistic Seismic Hazard Assessment (PSHA), which uses fault activity, maximum possible magnitudes, tectonics, lithology, and ground-shaking attenuation to estimate realistic earthquake risk.
All new infrastructure must follow the 2025 Earthquake Design Code, ensuring stronger, safer structures. The map also stresses urgent retrofitting of older buildings in Himalayan towns, especially schools, hospitals, and bridges.
