EARTHQUAKE DESIGN CODE, 2025

NEWS

• India has unveiled an updated seismic zonation map under the revised Earthquake Design Code, 2025 (IS 1893) by the Bureau of Indian Standards (BIS).
• This marks the most significant overhaul of seismic hazard assessment in decades, with major implications for urban planning, infrastructure, and disaster preparedness.

HIGHLIGHTS

What Has Changed in the New Seismic Map

• Introduction of a new highest-risk category – Zone VI.
• 61% of India’s landmass, housing nearly 75% of the population, now falls under moderate-to-high seismic risk zones.
• The entire Himalayan belt (J&K to Arunachal Pradesh), earlier split between Zones IV and V, is now uniformly classified as Zone VI, recognising its extreme tectonic vulnerability.
• Boundary regions between earlier zones are automatically upgraded to the higher-risk category, reducing underestimation of hazards.

Scientific Basis of the Revision

• Shift from historical-event-based zoning to Probabilistic Seismic Hazard Assessment (PSHA).
• PSHA evaluates:
  • Probability of earthquakes
  • Expected intensity of ground shaking
  • Fault behaviour, tectonics, and lithology
• Introduction of Probabilistic Exposure and Multi-Hazard Assessment (PEMA) to factor in:
  • Population density
  • Infrastructure concentration
  • Urban expansion and socio-economic vulnerability

Addressing Structural and Non-Structural Risks

• Earlier focus was mainly on Structural Elements (SEs) like beams and columns.
• The 2025 code also mandates protection of Architectural Elements and Utilities (AEUs) such as:
  • Glass façades, lifts, ceilings
  • HVAC systems, power and water utilities
• This reduces casualties, service disruption, and economic losses during earthquakes.

Why India Is Highly Vulnerable

• Indian Plate continues to collide with the Eurasian Plate at ~5 cm/year.
• The Himalayas are geologically young and unstable, with major fault systems:
  • Main Central Thrust (MCT)
  • Main Boundary Thrust (MBT)
  • Himalayan Frontal Fault (HFF)
• Historical high-magnitude earthquakes (1897–1950) and recent seismic clusters highlight persistent risk.

Governance, SDGs and Way Forward

• Supports SDG 9 (Resilient Infrastructure) and SDG 11 (Sustainable Cities).
• BIS urges:
  • Mandatory seismic audits
  • Retrofitting of critical infrastructure
  • Revision of state building by-laws, especially in Himalayan states
• Aligns with the PM’s 10-Point Agenda for Disaster Risk Reduction, emphasising preparedness, technology, and enforcement.

Conclusion

• The revised quake map shifts India from reactive response to proactive risk reduction, embedding science-backed planning into national development.