BharatNotes Why this chapter matters for UPSC: Natural disasters — lightning, earthquakes, and tsunamis — are recurring Prelims and Mains themes in GS3 (Disaster Management). This chapter provides the physical science foundation behind disaster causation and connects directly to India's disaster governance framework: NDMA, NDRF, SDRF, the Sendai Framework, and India's early warning systems (INCOIS, Damini app).
PART 1 — Quick Reference Tables
India's Seismic Zones
| Zone | Risk Level | States / Regions Covered |
|---|---|---|
| Zone II | Lowest | Parts of south/central peninsular India (stable Deccan craton) |
| Zone III | Moderate | Parts of Gujarat (non-Kutch), UP, Bihar, Maharashtra |
| Zone IV | High | Delhi–NCR, Jammu & Kashmir (non-Himalayan), Ladakh, parts of UP/Bihar |
| Zone V | Highest | Himalayan states (HP, Uttarakhand), entire NE India, Kashmir Valley, Andaman & Nicobar, Kutch (Gujarat) |
~59% of India's total land area is classified as earthquake-prone (Zones III–V).
Major Earthquakes in India — Key Facts
| Earthquake | Year | Magnitude | Deaths | Significance |
|---|---|---|---|---|
| Bhuj, Gujarat | 2001 | Mw 7.7 | ~20,000 | Triggered creation of NDMA; Kutch is Zone V |
| Latur, Maharashtra | 1993 | Mw 6.2 | ~10,000 | Moderate magnitude but massive deaths due to poor construction |
| Uttarkashi, Uttarakhand | 1991 | Mw 6.8 | ~768 | Himalayan fault zone seismicity |
| Indian Ocean Tsunami | 2004 | Mw 9.1 | ~227,898 globally | Deadliest natural disaster of 21st century; 10,749 deaths in India |
| Nepal Earthquake | 2015 | Mw 7.8 | ~8,964 | Shaking felt across northern India; Himalayan seismic arc |
Lightning — India Statistics and Safety
| Parameter | Detail |
|---|---|
| Annual lightning fatalities in India | ~2,500/year (highest globally) |
| Most affected states | Bihar, UP, Odisha, Jharkhand, MP |
| Warning app | Damini (IMD) — alerts when lightning within 20 km |
| Campaign | Lightning Resilient India Campaign (LRIC) |
| Lightning rod inventor | Benjamin Franklin, 1752 |
| Building Code requirement | Lightning arresters mandatory on tall buildings |
PART 2 — Detailed Notes
Lightning — How It Forms
During thunderstorms, rapid updrafts and downdrafts cause collisions between ice crystals and water droplets, generating electrostatic charge separation. Positive charges accumulate at the top of clouds; negative charges concentrate at the base. When the potential difference becomes large enough, a massive electrostatic discharge occurs — either between cloud layers or between cloud and ground. This discharge is lightning, accompanied by rapid heating of air (up to 30,000 K) that causes the shock wave we hear as thunder.
Lightning Rod (Lightning Arrester): A tall metal rod (typically copper) fixed to the highest point of a building and connected to the earth via a thick copper conductor. It provides a low-resistance path for the lightning discharge to travel safely into the ground, preventing the current from passing through the building structure. Invented by Benjamin Franklin in 1752. The Indian National Building Code mandates lightning protection systems on all tall structures.
Lightning Safety Rules
- Stay indoors; avoid verandas, windows, and balconies during a thunderstorm
- Do not shelter under trees — trees are tall conductors and attract strikes
- Avoid open fields, hilltops, and water bodies
- Do not use wired telephones; mobile phones may be used indoors but avoid use in open areas
- If caught outdoors, crouch low with feet together and hands over ears — minimises ground current path through the body
- Avoid touching metal fences, pipes, or electrical poles
UPSC GS3 — Lightning as a Disaster: India records approximately 2,500 lightning-related deaths annually — the highest globally — making it a significant but under-recognised disaster. Bihar and Uttar Pradesh are most affected due to flat terrain, exposure during agricultural activities, and lack of warning infrastructure.
Damini App (IMD): Provides hyperlocal lightning alerts — warns users when lightning is detected within a 20 km radius, giving 30–45 minutes advance warning. Developed by IMD in partnership with IITM Pune and Earth Networks.
Lightning Resilient India Campaign (LRIC): Launched by IMD and NDMA to create awareness, train gram panchayats, and push for early warning dissemination at village level.
Policy gap: Lightning is not classified as a "notified disaster" under the Disaster Management Act 2005, which means affected families cannot claim ex-gratia from State Disaster Response Funds (SDRF) — a longstanding demand for reclassification.
Earthquakes — Causes and Seismic Waves
Earthquakes occur when stress accumulated at tectonic plate boundaries is suddenly released, causing the ground to rupture along a fault. The point within the earth where rupture begins is the focus (hypocenter); the point directly above it on the surface is the epicentre. Three types of seismic waves are generated:
- P-waves (Primary / Longitudinal): Fastest; can travel through solids and liquids; cause compression and rarefaction; arrive first at seismograph stations
- S-waves (Secondary / Transverse): Slower; travel only through solids; cause shear motion perpendicular to direction of travel; more destructive than P-waves
- Surface waves (Love and Rayleigh waves): Slowest; travel along Earth's surface; most destructive — cause rolling, shaking motion that collapses buildings
Richter Scale vs Moment Magnitude Scale (Mw): The Richter scale measures local magnitude from seismograph amplitude — logarithmic (each whole number = ~10× amplitude, ~31× energy). For large earthquakes (above Mw 7), the Moment Magnitude Scale (Mw) is now the scientific standard as it accurately represents energy release across all sizes. Mw 7.7 (Bhuj) released energy equivalent to thousands of nuclear bombs.
India's Seismic Vulnerability
India lies at the collision boundary of the Indo-Australian plate and the Eurasian plate — the ongoing collision continuously builds stress in the Himalayas and NE India. The Andaman & Nicobar Islands sit on the subduction zone of the Eurasian plate. Key facts:
- Zone V covers the most seismically active regions: entire Northeast India, Kashmir Valley, Himalayan states of HP and Uttarakhand, Andaman & Nicobar, and Kutch district of Gujarat
- The Deccan Plateau (peninsular India) sits on a relatively stable craton — lower seismicity — but intraplate earthquakes do occur (Latur 1993 was intraplate)
- Latur demonstrated that moderate-magnitude earthquakes can be catastrophic if construction quality is poor — unreinforced masonry (stone and mud walls) collapsed entirely
UPSC GS3 — Earthquake-Resistant Construction: The Bureau of Indian Standards (BIS) prescribes IS codes for earthquake-resistant construction based on seismic zone. Key elements: reinforced concrete frames, seismic isolation bearings, shear walls, and proper foundation design. The National Building Code of India 2016 incorporates zone-wise seismic design requirements.
Retrofitting: Strengthening existing buildings without demolishing them — critical for India's large stock of unreinforced masonry structures in Zone IV/V cities. NDMA issues guidelines on retrofitting priorities.
Construction quality and enforcement: The Latur and Bhuj disasters revealed that IS codes existed but were not enforced. Building regulation, inspection, and construction quality remain primary challenges.
Tsunamis
Underwater earthquakes (magnitude > 6.5, shallow focus, vertical fault displacement) displace the ocean floor, pushing enormous volumes of water upward — generating tsunamis. In deep ocean, tsunami waves travel at ~800 km/h but have low amplitude (~1 m); as they enter shallow coastal water, they slow down but pile up in height (shoaling effect), reaching 10–30 metres at the coast.
Indian Ocean Tsunami, December 26, 2004:
- Triggered by Mw 9.1 earthquake on the Sumatra-Andaman subduction fault
- ~227,898 deaths across 14 countries — deadliest natural disaster of the 21st century
- India: ~10,749 deaths concentrated in Tamil Nadu, Andhra Pradesh (now AP + Telangana coast), Kerala, and Andaman & Nicobar Islands
- The disaster exposed India's complete absence of a tsunami early warning system
UPSC GS3 — Disaster Early Warning Systems: INCOIS (Indian National Centre for Ocean Information Services), Hyderabad: Operates the Indian Ocean Tsunami Warning System (IOTWS), established after the 2004 tsunami. Seismographs detect P-waves; DART (Deep-ocean Assessment and Reporting of Tsunamis) buoys confirm wave propagation; warnings issued within 7–10 minutes of an earthquake. INCOIS also provides storm surge warnings, high-wave alerts, and ocean state forecasts.
Seismograph early warning logic: P-waves travel faster than S-waves and surface waves. Detecting P-waves can provide seconds to a few minutes of warning before destructive waves arrive — enough time for automated alerts, train braking systems, and public sirens.
Sendai Framework for Disaster Risk Reduction (2015–2030): Adopted at the 3rd UN World Conference on Disaster Risk Reduction. Four priorities: Understanding disaster risk; Strengthening governance; Investing in DRR; Enhancing preparedness. India is a signatory. NDMA is the nodal agency.
India's Disaster Management Architecture
UPSC GS3 — NDMA and DM Act 2005: Disaster Management Act, 2005: Enacted following the Bhuj earthquake and 2004 tsunami experience. Established a three-tier structure:
- National Disaster Management Authority (NDMA): Apex body; PM as ex-officio Chairperson; lays down policies, plans, and guidelines
- State Disaster Management Authorities (SDMAs): Headed by Chief Ministers
- District Disaster Management Authorities (DDMAs): Headed by District Collectors/Magistrates
NDRF (National Disaster Response Force): 16 battalions (each ~1,149 personnel) drawn from paramilitary forces (BSF, CRPF, CISF, ITBP, SSB, Assam Rifles). Trained in search-and-rescue, medical first response, CBRN response.
SDRF (State Disaster Response Force): State-level rapid response teams; funded partly by the State Disaster Response Fund (SDRF — the financial mechanism). Norms for ex-gratia payments for different disasters set by the Finance Commission.
Finance Commission and disaster funding: The 15th Finance Commission (2021-26) provided for separate NDRF and SDRF pools; states can spend SDRF on notified disasters. The 12 notified disasters under MHA guidelines are: Cyclone, Drought, Earthquake, Fire, Flood, Tsunami, Hailstorm, Landslide, Avalanche, Cloudburst, Pest attack, and Frost/cold waves. Notable gap: Lightning is NOT a notified disaster despite causing ~2,500 deaths/year -- victims cannot claim SDRF ex-gratia; a reform demanded by state governments and NDMA task forces.
DM (Amendment) Act 2025: Received presidential assent 29 March 2025, in force 9 April 2025 — the first significant legislative update to the DM Act 2005 framework. Key features: creation of Urban Disaster Management Authority (UDMA) for state capitals and large cities; establishment of a National Disaster Database; statutory status to the National Crisis Management Committee (NCMC); integration of heatwaves and urban flooding into urban master plans; mandates periodic national/state disaster risk assessments incorporating climate-related risks. Heatwaves still not formally notified as a "disaster" under the SDRF list; 16th Finance Commission (report submitted October 2025, applicable FY 2026-27 onwards) recommendations on this front are being considered.
[Additional] 11a. Barren Island Volcano — India's Only Active Volcano
The chapter covers earthquakes (Indo-Australian Plate collision with Eurasian Plate) and tsunamis (Sumatra subduction) but entirely omits volcanoes -- another major natural phenomenon. India has an active volcano, and its tectonic mechanism connects directly to the plate tectonics already described.
Volcanoes — Formation: A volcano forms where magma (molten rock from the Earth's mantle) finds a pathway to the surface. This happens:
- At divergent plate boundaries: Plates pull apart; magma fills the gap (Mid-Atlantic Ridge, East Pacific Rise)
- At convergent/subduction boundaries: One plate dives under another; the descending plate melts; magma rises through the overlying plate to form a volcanic arc
- At hotspots: Plumes of extremely hot mantle material burn through a plate (Hawaii, Yellowstone)
India's Deccan Plateau is a remnant of a massive hotspot eruption ~66 million years ago (Deccan Traps -- possibly contributing to the mass extinction event that ended the dinosaurs), but no hotspot-driven volcanic activity exists in India today.
[Additional] Barren Island -- India's Only Active Volcano -- GS3 (S&T / Physical Geography):
| Feature | Data |
|---|---|
| Location | Andaman Sea, ~138 km northeast of Port Blair, Andaman and Nicobar Islands (Union Territory) |
| Status | India's only active volcano; only active volcano in the chain from Sumatra to Myanmar |
| Height | 354 m above sea level; rises ~2,250 m from the ocean floor |
| Habitation | Uninhabited island |
| First recorded eruption | 1787 |
| Tectonic setting | Indian Plate subducting under the Burma Plate (distinct from the Himalayan collision where Indo-Australian Plate collides with Eurasian Plate -- this is a separate subduction zone to the east) |
Recent activity:
- Since January 2022, Barren Island has been in a near-continuous eruptive state -- lava flows, ash plumes reaching 7,000-10,000 ft, Strombolian-type eruptions (lava fountaining from the central vent)
- Multiple eruption episodes confirmed in 2024-25 (Smithsonian Global Volcanism Program)
- Being uninhabited, the eruptions pose no direct human risk; ISRO and Indian Navy monitor via satellite imagery and aerial surveys
Narcondam Island (contrast):
- Also in the Andaman and Nicobar Islands
- A dormant volcano -- last erupted ~500,000-1 million years ago; no historic eruption recorded
- Home to the Narcondam Hornbill (Rhyticeros narcondami) -- Critically Endangered; endemic to this single island
UPSC significance:
- Barren Island appears regularly in Prelims as India's physical geography -- "India's only active volcano"
- The tectonic distinction is important: Himalayas = collision (no subduction), Barren Island = subduction (Indian Plate goes under Burma Plate) -- two different types of convergent plate boundaries
- Also tested in context of A&N Islands, tectonic settings, volcanic hazards, and geologically recent activity
[Additional] 11b. Earthquake Early Warning Systems — The Race Against Seismic Waves
The chapter explains P-waves and S-waves, seismic zones, and the NCS seismograph network. It does not close the loop on why P-wave speed matters practically: those seconds between P-wave arrival and destructive S-wave arrival are the entire basis of Earthquake Early Warning (EEW) systems — a current GS3 topic connected to India's NCS, Google's 2023 India launch, and ISRO's satellite-based alerts.
Key Terms — Earthquake Early Warning:
| Term | Meaning |
|---|---|
| Earthquake Early Warning (EEW) | System that detects the P-wave (fast, less destructive) at seismograph sensors near the epicentre, computes magnitude and location within seconds, and sends an electronic warning that travels at light speed — arriving at distant cities before the slower but destructive S-waves and surface waves |
| P-wave (Primary wave) | Longitudinal/compressional wave; travels at ~6–8 km/s through rock; arrives first; causes vertical ground motion; much less destructive than S-waves |
| S-wave (Secondary/Shear wave) | Transverse wave; travels at ~3–4 km/s (about half P-wave speed); arrives second; causes horizontal shaking; far more destructive to buildings; cannot travel through liquids |
| Warning time window | The time difference between P-wave detection and S-wave arrival at a distant city; a city 100 km from the epicentre could receive ~15–25 seconds of warning; 250 km from epicentre → ~40–60 seconds of warning |
| NCS (National Centre for Seismology) | Under Ministry of Earth Sciences (MoES); operates India's National Seismological Network; expanded from 80 stations in 2014 to >160 stations by February 2025 |
| Google Android Earthquake Alert System | Launched in India September 2023; uses smartphone MEMS accelerometers as a distributed sensor network; 2 alert levels: "Be Aware" (MMI 3–4) and "Take Action" (MMI 5+, bypasses Do Not Disturb); deployed to 98 countries by 2024 |
[Additional] Earthquake Early Warning — Physics, India's Status, and Google AEA (GS3 — Science and Technology / Disaster Management):
The science — why EEW works:
| Wave type | Speed | Damage potential | Role in EEW |
|---|---|---|---|
| P-wave | ~6–8 km/s | Low (vertical jolt) | Detected first; triggers the EEW alert computation |
| S-wave | ~3–4 km/s | High (horizontal shaking — causes most building collapse) | What EEW warning is trying to reach people before |
| Surface waves | ~2–4 km/s | Very high (long duration shaking; strongest amplitudes) | Arrives last; most felt at far distances |
| Electronic signal | ~300,000 km/s (light speed) | — | Carries the warning to phones/TV/sirens; vastly faster than all seismic waves |
Warning time calculation:
| Distance from epicentre | Approximate warning time |
|---|---|
| 50 km | 5–10 seconds |
| 100 km | ~15–25 seconds |
| 200 km | ~35–50 seconds |
| 300 km | ~55–75 seconds |
Even 10–20 seconds is enough for critical actions: trains auto-brake; elevators stop and open doors; surgeons pause operations; people adopt drop-cover-hold-on posture; gas valves close.
EEW ≠ Earthquake Prediction:
| EEW (Early Warning) | Earthquake Prediction |
|---|---|
| Earthquake has already started | Earthquake has not yet happened |
| Warning sent as P-wave detected (seconds after rupture) | Would require predicting hours/days/years before rupture |
| Technically feasible — operational in Japan, Mexico, US, China | NOT currently possible with any science — no reliable predictive method exists |
| Saves lives through immediate action (seconds of warning) | Would theoretically save more lives — but remains beyond current science |
India's EEW status:
| Parameter | Detail |
|---|---|
| NCS seismograph network | >160 stations as of February 2025 (PIB data; expanded from 80 in 2014) |
| Public EEW system | No fully operational public EEW system as of May 2026 |
| Pilot project | NCS has a pilot EEW project for the NW Himalayan region (most seismically active; Delhi in Seismic Zone IV is ~250–350 km from the Main Himalayan Thrust) |
| Status | Described as "nascent stage" in MoES parliamentary responses |
| Google AEA | Complements NCS — uses smartphone accelerometers as a distributed network; covers areas between seismograph stations |
Google Android Earthquake Alert System (AEA) — India launch:
| Parameter | Detail |
|---|---|
| India launch | September 2023 |
| How it works | Smartphone MEMS accelerometers detect ground motion; when multiple stationary, plugged-in phones in the same area simultaneously sense shaking, Google's servers triangulate epicentre and magnitude |
| Alert Level 1: "Be Aware" | MMI intensity 3–4 shaking; magnitude ≥ M 4.5; standard notification |
| Alert Level 2: "Take Action" | MMI intensity 5+ shaking; magnitude ≥ M 4.5; loud alarm that bypasses Do Not Disturb |
| Global rollout | 98 countries by 2024 |
| India user survey | 79% of ~1.5 lakh Indian users found alerts "highly useful" |
| Limitation | False alarms from vibrations (heavy footstep, construction); cannot replace dedicated seismographs; limited to areas with dense smartphone usage |
Global EEW systems — benchmarks:
| Country | System | Coverage | Warning time (major earthquake) |
|---|---|---|---|
| Japan | J-Alert / JMA (Japan Meteorological Agency) | Nationwide | 5–10 seconds for Tokyo in a Mw 7+ near Sagami Trough |
| Mexico | SASMEX | Mexico City + coastal zones | 60–90 seconds for Mexico City from subduction-zone events (oldest public EEW system, since 1991) |
| USA | ShakeAlert (USGS) | West Coast (California, Oregon, Washington) | Variable; ~10–60 seconds for coastal cities |
| China | CENC-EEW | Nationwide | 10–30 seconds for major urban centres |
| India | Pilot (NCS) | NW Himalayas only | Pilot stage; no public alerts yet |
UPSC synthesis: Key exam facts: EEW detects P-wave (fast, less destructive) and sends warning before S-wave (slow, destructive) arrives; P-wave speed = ~6–8 km/s; S-wave = ~3–4 km/s (about half P-wave speed); 100 km from epicentre = ~15–25 seconds warning; EEW ≠ earthquake prediction (prediction = before rupture; EEW = after rupture but before destructive waves arrive at far locations); NCS = Ministry of Earth Sciences = >160 stations (2025); India has no operational public EEW yet (pilot for NW Himalayas only); Google Android Earthquake Alert System launched in India = September 2023 = 98 countries = 2 alert levels (Be Aware / Take Action); Japan's J-Alert and Mexico's SASMEX (since 1991) = gold standard EEW systems. Prelims trap: EEW is NOT earthquake prediction (prediction = before the earthquake starts — currently impossible; EEW = seconds after it starts, before destructive waves reach distant cities); INCOIS handles tsunami early warning (ocean wave from underwater quake); NCS/MoES handles seismic (ground shaking) early warning — two different systems, two different agencies, frequently confused; Google Earthquake Alert uses smartphone MEMS accelerometers (NOT seismographs — the phones become a distributed sensor network); S-waves travel at ~half the speed of P-waves — this speed difference is the entire basis of EEW.
Exam Strategy
Prelims traps:
- P-waves travel through both solids and liquids; S-waves travel only through solids — this is how scientists infer the liquid outer core of the Earth
- The epicentre is on the surface; the focus/hypocenter is inside the Earth — do not confuse
- Richter scale is logarithmic: Mw 7 releases ~31× more energy than Mw 6, not just 10×
- INCOIS is in Hyderabad (not Chennai or Mumbai) — a frequent trap
- The 2004 Indian Ocean Tsunami epicentre was off the Sumatra coast (Indonesia), not India — but India was severely impacted
- Lightning is not a notified disaster under DM Act 2005 — victims cannot claim SDRF ex-gratia (a reform demanded)
- NDMA Chairman = Prime Minister (ex-officio) — Vice-Chairperson is a Cabinet Minister-rank appointee
Mains angles:
- India's disaster mortality vs economic loss — improving early warning but not last-mile dissemination
- Urban earthquake risk: Delhi in Zone IV, Mumbai in Zone III — unplanned construction and poor enforcement
- Sendai Framework targets and India's DRR progress
Practice Questions
Prelims:
Which of the following statements regarding the National Disaster Management Authority (NDMA) is correct?
(a) It is headed by the Home Minister of India
(b) It was established under the Civil Defence Act, 1968
(c) The Prime Minister of India is its ex-officio Chairperson
(d) It exclusively handles flood and drought disastersConsider the following about seismic waves:
- P-waves can travel through both solids and liquids
- S-waves travel faster than P-waves
- Surface waves are the most destructive
Which of the above is/are correct?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2, and 3
- P-waves can travel through both solids and liquids
The 'Damini' app, sometimes seen in the news, is related to:
(a) Flood early warning for river basins
(b) Cyclone track prediction
(c) Lightning alert and early warning
(d) Earthquake monitoring and real-time alerts
Mains:
What are the main causes of earthquake disasters in India? Discuss the structural and governance measures needed to reduce earthquake risk in Indian cities. (CSE Mains 2021, GS Paper 3, 15 marks)
The Indian Ocean Tsunami of 2004 was a turning point in India's disaster management architecture. Critically examine the changes made since then and assess their adequacy. (CSE Mains 2019, GS Paper 3, 15 marks)
