Introduction
Around 59% of India's landmass is vulnerable to moderate to severe seismic hazards, falling within Seismic Zones III to V. Earthquake risk across the subcontinent arises from a convergence of active plate tectonics, geological site conditions, and high socio-economic vulnerability marked by dense populations and unengineered built environments.
Drivers of Seismic Vulnerability in the Indian Subcontinent
- Active Inter-Plate Tectonics (Himalayan Arc): The Indian Plate continuously collides with the Eurasian Plate at a rate of approximately 45 to 50 mm per year, causing massive tectonic strain accumulation. Periodic releases of locked stress along major regional thrust systems—such as the Main Central Thrust (MCT) and Main Boundary Thrust (MBT)—result in high-magnitude earthquakes across the fragile Himalayan region (e.g., the 2015 Nepal earthquake of M7.8 and 2023 Jajarkot earthquake of M6.4).
- Peninsular Seismicity and Intra-Plate Faults: Although historically regarded as a stable cratonic shield, peninsular India experiences significant intra-plate earthquakes. Compressive stresses transmitted from the plate boundary reactivate ancient rift zones and subsurface faults (e.g., 1993 Latur M6.2 and 2001 Bhuj M7.7 earthquakes).
- Alluvial Amplification and Soil Liquefaction: The thick, unconsolidated, water-saturated Quaternary sediment layers in the Indo-Gangetic and Brahmaputra plains amplify seismic ground motion. Shaking induces soil liquefaction—a state where saturated granular soils temporarily lose shear strength and behave as a viscous fluid—causing heavy buildings to sink, tilt, or collapse in densely populated river basins like Delhi-NCR and North Bihar.
- Structural and Socio-Economic Fragility: Unregulated urban growth, rapid construction on unstable hill slopes, inadequate building code compliance, and high population density transform moderate ground shaking into catastrophic humanitarian disasters.
Measures Required to Reduce Earthquake Risk
- Strict Enforcement of Building Standards: Mandate compliance with the National Building Code (NBC) 2016 and Bureau of Indian Standards (BIS) seismic codes (IS 1893) for all new public and private constructions through municipal oversight and third-party engineering audits.
- Targeted Seismic Retrofitting: Undertake systematic structural retrofitting of critical lifeline infrastructure—including hospitals, schools, power stations, bridges, and dams—prioritising high-risk Zones IV and V in accordance with Priority 4 of the Sendai Framework for Disaster Risk Reduction.
- High-Resolution Seismic Microzonation: Conduct microzonation studies for all major urban agglomerations to identify fault traces, local ground amplification factors, and liquefaction-prone pockets, integrating these outputs directly into municipal land-use and developmental master plans.
- Early Warning and Monitoring Infrastructure: Expand the real-time telemetry network of the National Center for Seismology (NCS) and scale up regional earthquake early warning (EEW) systems, disseminating actionable alerts via platforms like the BhooKamp mobile application and automated siren systems.
- Institutional Readiness and Community Empowerment: Train local community first responders through initiatives like the Aapda Mitra scheme and conduct regular multi-agency simulation exercises involving the National Disaster Response Force (NDRF), State Disaster Response Forces (SDRF), and civil defence personnel.
Conclusion
While earthquakes are inevitable natural phenomena, disasters are largely preventable through systemic planning. Shifting focus from post-disaster response to comprehensive pre-disaster risk reduction—as articulated in the Prime Minister's 10-Point Agenda on Disaster Risk Reduction—is essential to building a seismically resilient subcontinent.