India’s New Earthquake Zonation Map
Why in news?
India released a revised seismic zonation map in 2025 under the updated Earthquake Design Code by the Bureau of Indian Standards (BIS)
Key Changes
- Added new Zone VI as highest-risk category, covering entire Himalayan arc (previously split into IV/V).
- Uses probabilistic seismic hazard assessment (PSHA) based on faults, magnitudes, tectonics, and soil type, not just history.
- Boundary towns auto-shift to higher zone; 61% land now moderate-high risk (up from 59%).
- Minor tweaks in stable southern peninsula areas.
Comparison with Previous Map
| Aspect |
Previous (IS 1893:2016) |
New (BIS 2025) |
| Zones |
II, III, IV, V |
Adds Zone VI; 4-6 total |
| Himalayan Coverage |
Split IV/V |
Entire arc in VI |
| Land in High Hazard |
59% moderate-high |
61% moderate-high |
| Methodology |
Historical data, boundaries |
PSHA with faults, lithology |
| Boundary Towns |
Varied by admin lines |
Auto higher-risk |
Implications
- Stricter building codes for homes, hospitals, bridges to handle shaking, liquefaction, and faults.
- Covers 75% population in active zones; mandates retrofitting in Himalayas.
- Factors population density and vulnerability for better planning.
Download Pdf
