Why in News: On July 10, 2025, a 4.4 magnitude earthquake shook Delhi, exposing the capital’s fragile infrastructure and lack of seismic preparedness.
Seismic Zone Classification:
Delhi lies in Zone 4 of India’s earthquake hazard map — the second-highest risk category.
Basis of Classification:
- The zoning is based on the MSK Scale (Medvedev-Sponheuer-Karnik scale), which assesses earthquake intensity rather than magnitude.
- Zone 4 corresponds to MSK VIII (8) level intensity. This level can cause significant structural damage, especially to poorly constructed buildings.
Recent Seismic Trends
- In the past five years, Delhi and surrounding areas have recorded multiple low-magnitude earthquakes (mostly in the 2.0–3.0 range).
- While these tremors were too weak to be felt by most people, they were detected by seismometers.
What is an Earthquake?
- An earthquake is the sudden shaking of the ground caused by the movement of tectonic plates beneath the Earth’s surface. This movement occurs when two blocks of the earth suddenly slip past each other along a fault line.
Key Terms
Hypocenter (Focus):
- The point within the Earth’s crust where the earthquake originates.
Epicenter:
- The point on the Earth’s surface directly above the hypocenter.
India’s Earthquake Vulnerability
- 58.6% of India’s landmass is vulnerable to moderate to very high intensity earthquakes.
- The Bureau of Indian Standards (BIS) has created a Seismic Zonation Map to classify earthquake-prone areas.
- India is divided into four seismic zones: Zone II, III, IV, and V.
Seismic Zones in India
Zone V (Very High Risk)
- Includes: Northeast India, Himachal Pradesh, Uttarakhand, parts of Bihar and Gujarat.
- Corresponds to MSK IX or higher intensity.
- These areas are most prone to severe earthquakes.
Zone IV (High Risk)
- Includes: Delhi, parts of Maharashtra, Jammu & Kashmir.
- Likely to experience MSK VIII level intensity.
- High potential for structural damage in urban areas.
Zone III (Moderate Risk)
- Includes: Parts of southern and central India.
- Experiences moderate seismic activity.
Zone II (Low Risk)
- Includes: Some regions of southern India.
- Least vulnerable to seismic events.
Why Delhi Is Seismically Vulnerable
1. Location in Seismic Zone IV
- Delhi is classified under Seismic Zone IV (second-highest risk) on India’s earthquake hazard map, implying it can experience earthquakes up to MSK VIII (heavy damage intensity) .
- This classification reflects the city’s high seismic threat level.
2. Multiple Active Fault Lines
The region sits on or near several active fault systems:
- Delhi–Haridwar Ridge
- Mahendragarh–Dehradun Fault
- Moradabad Fault
- Sohna Fault, among others .
These faults have historically generated moderate quakes (~M 6.5–6.8) .
3. Proximity to the Himalayan Collision Zone
- Although separated by 200–300 km, the ongoing collision between the Indian and Eurasian plates continues to build seismic stress that can propagate into Delhi .
4. Shallow and Frequent Tremors
- Delhi has experienced hundreds of small tremors (magnitude 1.1–4.6) over the last few decades—most too weak to feel but recorded by seismometers .
- The shallow depth (5–10 km) of these quakes makes shaking feel stronger than magnitude alone would suggest .
5. Soft Soil Amplifies Shaking
- Much of Delhi is built on soft alluvial soil, which amplifies seismic waves, causing buildings to shake more than they would on rock .
6. Rapid Urbanisation and Pre-code Buildings
- A dense population and rapid, often unregulated urban growth have led to:
- Many pre-2000 buildings built without seismic standards .
- Structural vulnerabilities like soft stories, weak reinforcement, and lack of retrofitting .
Possibility of a Large Earthquake in Delhi
Historical Earthquakes:
- 1720: A strong earthquake was reported in Delhi.
- 1803: An earthquake believed to have damaged the Qutub Minar; later identified to have originated near Srinagar-Devprayag in Uttarakhand.
Local Tectonic Setup:
- Delhi’s geological structure lacks major fault lines capable of generating high-magnitude earthquakes.
- No significant stress build-up zones exist beneath Delhi to trigger large local quakes.
External Threat from Himalayas:
- The city remains vulnerable to strong earthquakes originating in the Himalayan region.
Such quakes can cause serious damage in Delhi due to:
- Dense population
- Poorly retrofitted buildings
- High-rise and old infrastructure
Global Lessons and Best Practices
- Bangkok, despite a lower seismic risk, has updated its seismic code since 2007, using high-strength concrete and ductile detailing.
- Myanmar suffered higher casualties in 2025 due to unenforced building codes.
- India must tailor region-specific solutions — for example, steel jacketing for old buildings in Delhi, base isolation in Guwahati, and floodplain restrictions near the Brahmaputra.
Key Initiatives to Minimize Earthquake Risks
Seismic Monitoring:
- IMD monitors seismic activity and provides real-time alerts.
Zonation:
- GSI maps seismic zones; India reduced zones from five to four after Gujarat earthquake.
NDMA Guidelines:
- Issued national guidelines for earthquake management and conducts awareness campaigns.
Building Codes:
- BIS, BMTPC, HUDCO, and NDMA have set codes for earthquake-resistant construction based on seismic microzonation.
Smart Cities Focus:
- Emphasis on quake-resistant infrastructure in urban development.
International Collaboration:
- India founded CDRI to promote global cooperation on disaster-resilient infrastructure.
Way Forward: From Vulnerability to Resilience
1. Enforce seismic codes like IS 1893:2016 strictly.
2. Retrofit old buildings, especially schools and hospitals.
3. Expand early warning systems to rural and high-risk zones.
4. Run nationwide awareness campaigns on earthquake preparedness.
5. Promote quake-resistant infrastructure and local emergency plans.
Can Earthquakes Be Predicted?
- Exact prediction is very difficult.
- What matters is preparedness
- Everyone should know safe spots at home, work, or outside.
- Mock drills and adherence to building codes save lives.
Japan is a proven model—frequent quakes, minimal damage due to strict safety measures.
Conclusion
Focus must shift from prediction to resilience. With proper planning, drills, and enforcement, loss of life and property can be minimized.
UPSC Relevance
- GS 1 (Geography): Seismic zones of India, earthquake-prone areas, tectonic activity.
- GS 3 (Disaster Management): Urban vulnerability, preparedness, building codes, risk mitigation.
Mains Practice question
Despite lying in a high seismic risk zone, Delhi remains underprepared for a major earthquake. Critically examine the vulnerabilities of Delhi’s urban infrastructure and suggest measures for enhancing seismic resilience.