A tectonic shift in thinking to build seismic resilience, Pg6

Key Highlights:

• Delhi experienced a 4.4 magnitude earthquake on July 10, 2025, exposing the fragility of its buildings.
• Over 80% of Delhi’s structures, especially pre-2000, do not meet seismic safety codes.
• India lies on an active tectonic boundary, with increasing seismic events across the region.
• The IS 1893:2016 seismic code is poorly enforced in high-risk cities like Delhi and Guwahati.
• Liquefaction-prone soils, poor retrofitting, and non-compliance elevate urban seismic risks.
• ₹50,000 crore is the estimated annual cost needed for retrofitting and seismic preparedness.

Detailed Insights:

• Delhi lies in Seismic Zone IV, with a Peak Ground Acceleration (PGA) of 0.24g, putting over 33 million residents at risk.
• Seismic vulnerability extends beyond Delhi, with the Northeast and Andaman-Nicobar in Seismic Zone V.
• Recent quakes in Myanmar, Tibet, Greece, and India-Myanmar border highlight a regional tectonic restlessness.
• Many high-rises in cities are not compliant with IS 1893:2016, which mandates ductile detailing and shear walls.
• Poorly designed structures in liquefaction-prone zones, like East Delhi, risk collapse during moderate-to-high magnitude quakes.
• Comparative global practices show that Bangkok’s updated seismic codes reduced damage, while Myanmar’s lax enforcement worsened outcomes.
• Guwahati needs deep pile foundations and base isolation for critical buildings, especially due to its proximity to the Brahmaputra floodplain.
• The Bhuj earthquake (2001) and Nepal quake (2015) remain warnings about the consequences of unpreparedness and poor planning.
• National Center for Seismology (NCS) offers real-time monitoring via the IndiaQuake app, but lacks rural outreach.
• Retrofitting measures like steel jacketing and deep pile foundations are essential for seismic resilience.
• Citizens must be sensitised about earthquake preparedness including emergency kits, safe evacuation, and community drills.

Scientific/Technical Concepts Involved:

• Seismic Zone Classification (II–V): A classification of Indian regions based on earthquake risk, with Zone V being the highest risk.
• Peak Ground Acceleration (PGA): Measures ground shaking severity; higher PGA indicates higher seismic risk.
• IS 1893:2016: Bureau of Indian Standards’ code for earthquake-resistant design of structures.
• Liquefaction: A phenomenon where saturated soil loses strength during seismic shaking, leading to structural collapse.
• Ductile Detailing: Engineering design practice ensuring that buildings deform without collapsing during quakes.
• Base Isolation: A seismic design technique that decouples a structure from ground motion, reducing earthquake impact.

Mains Mock Question:

Q. India’s urban centres are increasingly vulnerable to seismic disasters. Discuss the importance of seismic zoning, code enforcement, and retrofitting measures in ensuring earthquake resilience.