Earthquake Zones of India

India possesses a high vulnerability to seismic activity primarily due to the ongoing northward convergence of the Indian Tectonic Plate with the Eurasian Plate. This collision occurs at a rate of approximately 40 mm to 50 mm per year, causing immense structural strain along the Himalayan arc, the Indo-Gangetic plains, and extending into parts of the stable peninsular shield. According to the National Disaster Management Authority (NDMA), approximately 58.6% of India’s total landmass is prone to earthquakes of moderate to very high intensity (Modified Mercalli Intensity VII to X and above).

Institutional Framework and Classification Criteria

The Bureau of Indian Standards (BIS) is the apex national body responsible for publishing and updating the Seismic Zoning Map of India. The foundational standard for earthquake-resistant design is contained in the document IS 1893 (Part 1): 2016, titled “Criteria for Earthquake Resistant Design of Structures”.

Evolution of Seismic Zones

The seismic zonation of India has evolved scientifically over decades based on historical macroseismic data, tectonic features, and peak ground acceleration values.

• Historical Classification: Initially, the 1962 and 1970 versions of the BIS map divided India into five seismic zones (Zone I to Zone V).
• The 2002 Revision: Following severe damage anomalies observed during the 1993 Latur earthquake (which occurred in a supposedly stable Zone I region), the BIS merged Zone I into Zone II.
• Current Status: India is strictly divided into four seismic zones: Zone II, Zone III, Zone IV, and Zone V. There is no Zone I in the contemporary seismic catalog of India.

Seismological Evaluation Criteria

The zoning is determined by combining the macroseismic intensity observed during past earthquakes with the Maximum Considered Earthquake (MCE) parameters.

Note: The Zone Factor (Z) represents the effective peak ground acceleration that can be reasonably expected during the design life of a structure within that specific zone.

Comprehensive Breakdown of India’s Seismic Zones

Zone V: Very High Damage Risk Zone

Zone V is seismically the most active and vulnerable region in India, characterized by a Zone Factor of 0.36. It encompasses areas that have historically witnessed earthquakes of magnitude greater than 7.0 on the Richter scale or are tectonically predisposed to high-intensity shaking.

• Geographical Coverage: The entire Northeastern region of India (including the Seven Sister States), northern pockets of Jammu and Kashmir, the entire Union Territory of Ladakh, northern Himachal Pradesh, eastern Uttarakhand, the Rann of Kutch in Gujarat, parts of North Bihar (specifically districts bordering Nepal like Madhubani and Sitamarhi), and the Andaman and Nicobar Islands.
• Tectonic Drivers: The Himalayan Thrust Systems (Main Central Thrust, Main Boundary Thrust), the Indus-Tsangpo Suture Zone, the Owen Fracture Zone, and the active subduction zone in the Andaman Sea.

Zone IV: High Damage Risk Zone

Zone IV experiences severe shaking corresponding to an intensity of VIII on the Modified Mercalli scale, with a assigned Zone Factor of 0.24. Structures in this zone require stringent adherence to earthquake-resistant engineering codes.

• Geographical Coverage: The remaining parts of Jammu and Kashmir and Ladakh, the rest of Himachal Pradesh and Uttarakhand, Sikkim, northern parts of Uttar Pradesh (Indo-Gangetic plain regions), northern West Bengal (including the Dooars and Darjeeling), parts of western Gujarat, segments of Maharashtra (Koyna region), and the National Capital Territory (NCT) of Delhi.
• Tectonic Drivers: Shallow crustal faults within the Indo-Gangetic foreland basin, the Mahendragarh-Dehradun Sub-surface Fault, and localized shear zones in the western peninsular margins.

Zone III: Moderate Damage Risk Zone

Zone III represents areas prone to MSK intensity VII with a Zone Factor of 0.16. This zone serves as a transitional buffer between the highly active northern/coastal plate boundaries and the relatively stable interiors.

• Geographical Coverage: Kerala, Goa, Lakshadweep Islands, remaining parts of Uttar Pradesh, Gujarat, and West Bengal, parts of Punjab, Rajasthan, Madhya Pradesh, Bihar, Jharkhand, Chhattisgarh, Maharashtra, Odisha, Andhra Pradesh, Telangana, Tamil Nadu, and Karnataka.
• Key Cities Included: Mumbai, Kolkata, Chennai, Bengaluru, and Hyderabad are classified under Zone III due to intraplate lineaments and deep-seated structural rifts.

Zone II: Low Damage Risk Zone

Zone II is the seismically quietest region of India, possessing a Zone Factor of 0.10. It is largely associated with the rigid crystalline basement of the Peninsular Shield.

• Geographical Coverage: Central and southern parts of the Indian Peninsula, major interior portions of Madhya Pradesh, Odisha, Andhra Pradesh, Telangana, Karnataka, and Tamil Nadu.
• Seismic Nature: While classified as low risk, this zone is not completely immune to earthquakes. It is susceptible to intraplate earthquakes triggered by ancient fault reactivation along weak rift pillows.

Tectonic Anomalies and Major Historical Earthquakes

Intraplate Seismicity and Reservoir Triggered Seismicity (RTS)

The Indian Shield was historically considered an aseismic stable craton. However, two major phenomena have challenged this assumption:

• Reservoir Triggered Seismicity (RTS): The 1967 Koyna Earthquake (Magnitude 6.5) in Maharashtra is a premier global example of RTS, caused by the hydro-tectonic pressure changes beneath the Koyna Dam reservoir.
• Intraplate Earthquakes: The 1993 Latur Earthquake (Magnitude 6.2) occurred along the Tirna River fault within the stable Deccan Trap province, demonstrating that deep-seated crustal adjustments can cause severe damage far from plate boundaries.

Historic Seismic Catalog of India

High-Yield Trivia for Prelims Strategy

The Central Himalayan Seismic Gap

Seismologists have identified a major “Seismic Gap” in the Central Himalayas—a stretch between the rupture zones of the 1905 Kangra earthquake and the 1934 Bihar-Nepal earthquake. This specific segment has not experienced a major mega-thrust earthquake for over 300 years, indicating that the region has accumulated immense elastic strain energy and is highly vulnerable to a future high-magnitude seismic event.

Microzonation Studies

The Ministry of Earth Sciences (MoES) conducts Seismic Microzonation for major mega-cities in India (such as Delhi, Bengaluru, and Kolkata). Unlike macro-zonation maps, microzonation divides a specific urban area into smaller zones based on local geological factors like soil thickness, rock composition, water table depth, and ground response to pinpoint precise structural vulnerability.

Structural Mitigation Projects

The National Earthquake Risk Mitigation Project (NERMP) and the National Building Code (NBC) of India regulate the incorporation of ductile detailing in reinforced concrete structures, structural base isolation, and seismic dampers particularly for buildings located in Zone IV and Zone V.