Master10
Disaster Management & Climate Resilience Module

Earthquakes, Seismic Zonation & Landslides

The Indian subcontinent exhibits high seismic vulnerability resulting from the ongoing northward collision of the Indian tectonic plate into the Eurasian plate at a rate of approximately 4 to 5 centimetres per year. The Bureau of Indian Standards (BIS IS 1893:2016) classifies India into four seismic hazard zones: Zone II (Low), Zone III (Moderate), Zone IV (High), and Zone V (Very High), with the Himalayan arc, Northeast India, and the Rann of Kutch placed in Zone V. Seismic mitigation mandates earthquake-resistant construction conforming to national building codes, retrofitting critical infrastructure, and real-time seismic monitoring by the National Centre for Seismology. Additionally, hilly terrains in the Himalayas and Western Ghats face severe landslide hazards, mitigated through Geological Survey of India landslide zonation mapping.

Key Concepts & Examination Highlights

  • India is divided into four seismic zones by BIS: Zone II (least active) to Zone V (most active/highest risk); Zone I was merged into Zone II.
  • Zone V encompasses the entire North-Eastern region, parts of Jammu & Kashmir, Himachal Pradesh, Uttarakhand, Rann of Kutch, and Andaman & Nicobar Islands.
  • The National Centre for Seismology (NCS) under the Ministry of Earth Sciences maintains the National Seismological Network.
  • Geological Survey of India (GSI) launched the National Landslide Susceptibility Mapping (NLSM) program covering 0.42 million sq km.
  • Zone IV (High Damage Risk Zone) covers the Indo-Gangetic Plains, Delhi-NCR, parts of Jammu and Kashmir, Himachal Pradesh, Bihar, and northern Uttar Pradesh.
  • The 2001 Bhuj earthquake in Gujarat (magnitude 7.7 on January 26, 2001) was an intraplate earthquake that occurred along the Katrol Hill Fault and Kutch Mainland Fault.
  • Liquefaction is a phenomenon occurring during strong earthquake shaking where saturated, loose cohesionless soils lose shear strength and behave like a liquid.
  • The Indian Tsunami Early Warning Centre (ITEWC), established at INCOIS in Hyderabad following the December 2004 tsunami, provides real-time tsunami advisories for the Indian Ocean rim.
  • Landslides in the Western Ghats are primarily triggered by high-intensity monsoon rainfall on steep weathered slopes, whereas Himalayan landslides are driven by both heavy rainfall and tectonic fragility.
  • The National Building Code of India (NBC) and IS 1893 outline mandatory structural design codes for earthquake-resistant buildings and retrofitting.
  • The Main Central Thrust (MCT) and Main Boundary Thrust (MBT) are major active geological fault lines running along the Himalayan arc where significant seismic strain accumulates.
  • GSI operates a Landslide Early Warning System (LEWS) in experimental districts of West Bengal (Darjeeling) and Tamil Nadu (Nilgiris) using rainfall threshold models.
  • The Bureau of Indian Standards (BIS) classifies India into four seismic hazard zones: Zone II (Low), Zone III (Moderate), Zone IV (Severe), and Zone V (Very Severe).
  • Seismic Zone V covers the entire northeastern India, parts of Jammu & Kashmir, Ladakh, Himachal Pradesh, Uttarakhand, the Rann of Kutch in Gujarat, and Andaman & Nicobar Islands.
  • Seismic Zone IV encompasses the northern plains including Delhi, parts of Jammu & Kashmir, Himachal Pradesh, Uttarakhand, northern Bihar, and parts of Maharashtra.
  • The National Centre for Seismology (NCS) under the Ministry of Earth Sciences is the nodal agency for monitoring earthquake activity in and around India.
  • The Main Central Thrust (MCT), Main Boundary Thrust (MBT), and Himalayan Frontal Thrust (HFT) are major active tectonic fault systems accommodating India-Eurasia plate convergence.
  • Paleoseismology is the study of past prehistoric earthquakes through the examination of stratigraphic sediments, fault trenches, and seismic liquefaction features.
  • Liquefaction is a phenomenon where water-saturated, unconsolidated soil temporarily loses shear strength and behaves as a viscous liquid during severe earthquake shaking.
  • Landslides in India are predominantly triggered by intensive monsoon rainfall, slope toe cutting, deforestation, and seismic activity in Himalayan and Western Ghat regions.
  • The Geological Survey of India (GSI) is the national nodal agency for landslide hazard susceptibility mapping and operates the National Landslide Early Warning System.
  • The National Landslide Susceptibility Mapping (NLSM) project by GSI covers all hilly terrains of India at 1:50,000 scale to identify high-risk zones.
  • Soil bioengineering techniques, including deep-rooting vetiver grass planting and geo-textiles, are increasingly utilized for cost-effective hill slope stabilization.
  • Debris flows and rockfalls represent rapid mass movements of water-saturated sediment and rock fragments down steep slopes, common along Himalayan road corridors.
  • The National Building Code of India (NBC) and IS 1893 formulate earthquake-resistant design standards and seismic load calculation guidelines for civil structures.
  • An earthquake is the sudden release of accumulated strain energy in the Earth's lithosphere, generating seismic waves that propagate in all directions.
  • The Focus (Hypocenter) is the exact point within the Earth's crust where the seismic fracture initiates and strain energy is first released.
  • The Epicenter is the point on the Earth's surface situated vertically directly above the hypocenter.
  • Body waves travel through the interior of the Earth and are classified into Primary (P) waves and Secondary (S) waves.
  • P-waves (Compressional or Longitudinal waves) are the fastest seismic waves, capable of traveling through solids, liquids, and gases.
  • S-waves (Transverse or Shear waves) vibrate perpendicular to wave propagation and can only travel through solid materials, creating a seismic shadow zone beyond 105 degrees.
  • Surface waves travel along the Earth's surface and include Rayleigh (R) waves and Love (L) waves, which cause the most severe structural destruction during earthquakes.
  • The Richter Magnitude Scale, developed by Charles F. Richter in 1935, is a logarithmic scale measuring the total seismic energy released at the earthquake source.
  • Each whole unit increase on the logarithmic Richter scale corresponds to approximately a 31.6-fold increase in seismic energy released.
  • The Moment Magnitude Scale (Mw), introduced by Hiroo Kanamori and Thomas C. Hanks in 1979, is the standard modern scale used by seismologists for measuring large earthquakes.
  • The Modified Mercalli Intensity (MMI) Scale is a 12-point scale (I to XII) measuring the observed physical intensity and destructiveness of shaking at a specific surface location.
  • The Bureau of Indian Standards (BIS) IS 1893:2002 classifies India into four Seismic Hazard Zones: Zone II, Zone III, Zone IV, and Zone V.
  • Seismic Zone I was merged into Zone II in the revised 2002 zonation map, meaning no part of India is considered completely free from earthquake risk.
  • Seismic Zone V represents the Highest Risk Zone (Very High Damage Risk), corresponding to MMI intensity IX and above and a zone factor of 0.36.
  • Zone V covers the entire North-Eastern states, Jammu and Kashmir, Ladakh, Himachal Pradesh, Uttarakhand, the Rann of Kutch in Gujarat, northern Bihar, and Andaman & Nicobar Islands.
  • Seismic Zone IV represents the High Damage Risk Zone (MMI intensity VIII, zone factor 0.24), covering Delhi, remaining parts of J&K and Himachal, northern UP, Bihar, and West Bengal.
  • Delhi NCR is situated in Seismic Zone IV, making the national capital highly vulnerable to moderate-to-severe seismic shocks.
  • Seismic Zone III is the Moderate Damage Risk Zone (MMI intensity VII, zone factor 0.16), covering Mumbai, Kolkata, Chennai, and parts of the Peninsular shield.
  • Seismic Zone II represents the Low Damage Risk Zone (MMI intensity VI or less, zone factor 0.10), covering the remaining stable parts of the central and southern Deccan Plateau.
  • Nearly 59 percent of India's total land area is vulnerable to moderate to severe earthquakes (Seismic Zones III to V).
  • The Main Central Thrust (MCT), Main Boundary Thrust (MBT), and Himalayan Frontal Thrust (HFT) are major active seismic fault lines along the Himalayan convergent plate boundary.
  • The Indian Plate continues to collide northward with the Eurasian Plate at a rate of approximately 4 to 5 centimeters per year, causing immense strain accumulation.
  • The 1897 Great Shillong Earthquake (magnitude 8.1) in Meghalaya was one of the strongest intraplate continental earthquakes recorded in human history.
  • The 1905 Kangra Earthquake (magnitude 7.8) in Himachal Pradesh killed over 20,000 people and destroyed Kangra, Dharamshala, and surrounding towns.
  • The 1934 Bihar-Nepal Earthquake (magnitude 8.0) caused widespread liquefaction and severe destruction across northern Bihar and the Kathmandu Valley.
Curriculum & Reference Sources: Bureau of Indian Standards (BIS), National Centre for Seismology (NCS), Geological Survey of India (GSI), NDMA.

Sample Solved Questions & Concept Explanations

8 Verified Concept Questions
Q1.EASY

In which seismic hazard zone (as per Bureau of Indian Standards IS 1893:2016) is the entire North-Eastern region of India placed due to high tectonic activity?

Q2.MEDIUM

Why does the contemporary seismic zonation map of India (IS 1893) contain only Zones II, III, IV, and V, with no 'Zone I'?

Q3.HARD

The acute seismic vulnerability of the Himalayan mountain belt is fundamentally driven by which specific plate tectonic phenomenon?

Q4.EASY

What is the underground point inside the Earth's crust where an earthquake rupture originates called?

Q5.EASY

What is the point on the Earth's surface located directly vertically above the subterranean seismic focus?

Q6.EASY

Which scientific instrument is used to detect, record, and plot the amplitude and arrival times of seismic waves during an earthquake?

Q7.EASY

Which autonomous institute located in Hyderabad operates the Indian Tsunami Early Warning Centre (ITEWC) under the Ministry of Earth Sciences?

Q8.EASY

Which scale measures the intensity of an earthquake based on observable ground damage, structural collapse, and human perception rather than total energy released?