Cost Concerns Delay Safer Building Codes Despite Himalayan Threats

Syllabus: GS3/Disaster Management

Context

• India’s earthquake safety codes are under scrutiny after the government withdrew updated building standards backed by a decade of scientific research.

Background

• A decade of government-backed studies involving experts in seismology, geology, and structural engineering clearly indicate:
  • Existing seismic hazard assessments are outdated or conservative.
  • Potential earthquake damage to residential buildings, bridges and dams.
• The Bureau of Indian Standards withdrew updated earthquake-resistant design norms due to the concerns from Cabinet Secretariat that stricter norms would:
  • Increase project costs, Affect ongoing infrastructure (e.g., metro rail projects).

The IS 1893 ‘Criteria for Earthquake Resistant Design of Structures’

• It is a five-part document published by the Bureau of Indian Standards (BIS).
• It provides the mandatory guidelines that engineers and architects must follow to ensure buildings and infrastructure can survive seismic activity.
• India’s seismic zoning maps delineate the country into four zones (Zone 2II, III 3, IV4 and V5).
  • Zone 2 II is the calmest part of India’s seismic landscape.

Gaps in Earlier Zoning Framework

• Retrospective Zoning Approach: Earlier seismic zoning classified areas (Zone IV/V) only after major earthquakes, making it reactive rather than predictive.
• Underestimation of Seismic Gaps: Regions with pent-up tectonic strain but no recent earthquakes were wrongly treated as low-risk.
• Neglect of Local Soil Conditions: The framework ignored soil amplification effects, which can significantly increase ground shaking and structural damage.
• Underutilisation of Seismic Data: Data from 168 monitoring stations under the National Centre for Seismology was not fully incorporated into hazard assessments.
• Inadequate Scientific Methodology: Lack of adoption of Probabilistic Seismic Hazard Assessment (PSHA) led to incomplete and less accurate risk estimation.
• Short Seismic Record: India’s instrumental earthquake record is only about a century old, while historical records are patchy and incomplete, making long-term risk assessment difficult.

Highlights of New Standards

• Large Population at Risk: About 79% of India’s population lives in regions prone to moderate to severe earthquakes, highlighting the urgency of updated seismic standards.
• Higher PGA Values in New Map: Revised hazard map proposes significantly higher Peak Ground Acceleration values (up to 0.75 g), nearly doubling estimates in high-risk zones.
• Introduction of Zone VI: A new seismic Zone VI has been introduced for areas with PGA > 0.6 g, especially in the Himalayas and Northeast, improving risk differentiation.
• Improved Scientific Basis: The new assessment uses a large dataset (69,000+ earthquakes from 2600 BC–2019) and advanced probabilistic methodology, making it more reliable.
• Global Alignment: Revised PGA values align India with global practices, countries like Japan and the US often design for ~1 g or higher in high-risk regions.

Conclusion

• While the revised seismic map is scientifically robust and closer to reality, its implementation raises serious concerns about affordability, feasibility, and enforcement, creating a classic policy dilemma between safety and cost.

Source: TH