India has taken a critical step towards bolstering its disaster preparedness by releasing an updated national seismic zonation map. This revision, part of the newly launched Earthquake Design Code, 2025 (IS 1893) by the Bureau of Indian Standards (BIS), marks the most significant shift in the country's earthquake risk assessment in decades.
A Major Shift in Seismic Risk Classification
The revised map introduces a pivotal change: a new, highest-risk Zone VI. This reclassification dramatically alters the risk profile for the entire Himalayan belt. Previously divided between Zones IV (high) and V (very high), the entire mountain range, stretching from Jammu and Kashmir to Arunachal Pradesh, is now consolidated under Zone VI.
This long-overdue update acknowledges the profound and uniform tectonic vulnerability of the young, rising Himalayas. Consequently, 61% of India's landmass, which houses a staggering 75% of the country's population, now falls under moderate-to-high seismic hazard zones. This is an increase from the previous 59% of land area considered quake-prone.
Beyond Structural Safety: A Holistic Design Code
The 2025 code moves beyond traditional earthquake engineering, which focused primarily on Structural Elements (SEs) like beams and columns. It now mandates standards for protecting Architectural Elements and Utilities (AEUs)—non-structural components such as glass facades, ceilings, lifts, and air-conditioning ducts.
This holistic approach is vital because damage to AEUs during ground shaking can cause significant casualties, disrupt critical services, and lead to major socio-economic losses, especially in hospitals, schools, and government buildings. The revised provisions aim to minimize damage to both SEs and AEUs, aligning with UN Sustainable Development Goals 9 (resilient infrastructure) and 11 (sustainable cities).
The Science and Rationale Behind the Update
The new zonation is based on the Probabilistic Seismic Hazard Assessment (PSHA) method, a global scientific standard that evaluates both the likelihood and potential intensity of ground shaking. It incorporates comprehensive data on faults, tectonic movements, and ground behavior.
A key innovation is the introduction of the 'exposure window' concept, developed using the Probabilistic Exposure and Multi-Hazard Assessment (PEMA) method. This factors in population density, infrastructure concentration, and socio-economic vulnerability, ensuring that risk assessment considers human and economic impacts, not just geology.
The Indian Plate continues to push north into the Eurasian Plate at about 5 cm per year, keeping the Himalayan region in a state of constant tectonic stress. The presence of major fault systems like the Main Frontal Thrust (MFT) near densely populated foothills further elevates the risk, with potential for ruptures to extend into plains cities like Dehradun.
Implications for Urban Planning and Future Preparedness
The map's implications are far-reaching, particularly for Himalayan states now under Zone VI. It necessitates a comprehensive overhaul of building codes, infrastructure design norms, and long-term urban planning frameworks. The BIS has urged that all new construction adhere to the revised guidelines.
Mandatory seismic audits and retrofitting of vulnerable existing structures, especially critical and heritage buildings, become imperative. This focus on mitigation is crucial as earthquakes remain unpredictable. India's tragic history—from the 1897 Shillong quake to the 2001 Bhuj disaster that claimed nearly 13,000 lives—underscores the urgency. The nation recorded 159 earthquakes between November 2024 and February 2025 alone.
This revised seismic map, therefore, is not just a technical document but a foundational tool for implementing the Prime Minister's 10-Point Agenda for Disaster Risk Reduction. It aims to guide smarter, safer city building and enhance national resilience against inevitable future seismic events.
