Seismic zones of India

India's earthquake hazard is mapped into zones so that buildings in high-hazard areas are designed for larger forces. The map in IS 1893 (Part 1):2016 has four zones, numbered II to V, each with a zone factor that represents the effective peak ground acceleration, as a fraction of g, for the design earthquake. Zone II, the lowest, covers much of the stable peninsular shield; zone V, the highest, covers the regions closest to the most active plate-boundary faults.

The pattern follows geology. The Indian plate is moving north and pushing under Eurasia, so the Himalayan arc, the North-East and the Andaman and Nicobar Islands carry the highest hazard. The Kutch region in Gujarat has a history of large intraplate earthquakes and is also in the highest zone. The Indo-Gangetic plains, close to the Himalaya and underlain by deep soft sediments, fall largely in zones III and IV, and most of southern and central India is in zones II and III.

The zone factor enters the design horizontal seismic coefficient together with the importance of the building, the response reduction factor for its structural system and the spectral shape for its period and soil. Moving up one zone raises design forces substantially, which is why zone boundaries matter to cost as well as safety.

Hazard maps are revised as data improve. A revised edition of IS 1893 (Part 1) with a new probabilistic map was notified in late 2025 and withdrawn in March 2026, restoring the 2016 edition. Always confirm the edition and zone in force on the BIS portal before design; local site studies are needed for dams, nuclear plants and other critical works.