Identifying Earthquake-Prone Areas in India: Risks and Readiness

India sits on one of the most geologically active regions of the world, where tectonic forces have shaped not just towering mountain ranges but also a persistent earthquake threat. Understanding where these risks are highest and why they occur is essential for building safer communities and protecting lives across the nation.

Seismic regions in India 🔗

The Bureau of Indian Standards divides India into four seismic zones based on the intensity and frequency of earthquakes. These zones range from Zone II (lowest risk) to Zone V (highest risk), with approximately 59% of India’s landmass vulnerable to earthquakes of varying magnitudes.

Zone V: Very high damage risk 🔗

Coverage: About 11% of India’s total area falls under this most dangerous category. This zone includes the Kashmir Valley, Western and Central Himalayas, North-East India, parts of Bihar, the Rann of Kutch, and the Andaman and Nicobar Islands. Major cities like Srinagar and Guwahati are located in this zone, where earthquakes can exceed magnitude 7.0. The region has witnessed some of history’s most devastating tremors, including the 1897 Shillong earthquake (magnitude 8.7) and the 1950 Assam-Tibet earthquake (magnitude 8.6).

Zone IV: High damage risk 🔗

Coverage: Approximately 18% of India lies in this high-risk zone. The national capital Delhi falls under Zone IV, along with large portions of Jammu and Kashmir, Himachal Pradesh, Uttarakhand, parts of Punjab, and northern regions of Bihar and West Bengal. Buildings in this zone must be designed to withstand strong ground shaking with magnitudes typically ranging from 6.0 to 6.9.

Zone III: Moderate damage risk 🔗

Coverage: About 30% of India’s landmass is classified as Zone III. This includes major metropolitan areas such as Mumbai, Chennai, and Kolkata. The zone covers parts of Kerala, Goa, coastal regions of Andhra Pradesh and Odisha, and sections of the Indo-Gangetic plains. While earthquakes are less frequent here, the 1993 Latur earthquake (magnitude 6.4) demonstrated that even moderate-risk zones can experience significant destruction.

Zone II: Low damage risk 🔗

Coverage: The remaining 41% of India falls into the least seismically active zone. Cities like Bangalore, Hyderabad, Nagpur, and Jaipur are located here. Though earthquakes are rare, the zone is not entirely risk-free, and basic seismic safety measures are still recommended for construction.

Causes and mechanisms of earthquakes in India 🔗

The Indian plate collision 🔗

The primary cause of India’s high seismic activity is the ongoing collision between the Indian and Eurasian tectonic plates. About 50 million years ago, the Indian plate, which had broken away from the ancient supercontinent Gondwana, collided with the Eurasian plate. This monumental collision created the Himalayan mountain range and continues today as the Indian plate moves northward at approximately 5 centimeters per year.

The continuous convergence generates enormous stress along the plate boundary. When this accumulated stress exceeds the strength of rocks, it releases suddenly, causing earthquakes. The Himalayan region bears the brunt of this inexorable pressure, making it one of the most seismically active zones on Earth.

Major fault systems 🔗

Several major fault systems crisscross India, acting as zones where stress accumulates and releases. The Main Boundary Thrust (MBT) and the Main Central Thrust (MCT) run along the Himalayan foothills, while the Narmada-Son lineament cuts through central India. In western India, faults in the Rann of Kutch region have produced devastating earthquakes, including the 2001 Bhuj earthquake that killed over 20,000 people. These fault lines represent weak zones in Earth’s crust where movement is more likely to occur.

Factors influencing earthquake damage 🔗

Ground shaking intensity 🔗

The severity of ground shaking depends on several factors including earthquake magnitude, distance from the epicenter, and depth of the focus. Shallow earthquakes (occurring less than 70 kilometers deep) typically cause more intense surface shaking than deeper ones. The duration of shaking also matters-prolonged shaking, even at moderate intensities, can cause progressive damage to structures, leading to eventual collapse.

Soil characteristics 🔗

The type of soil beneath a building significantly affects how earthquake waves travel and amplify. Soft, loose soils such as alluvial deposits and filled land can amplify ground motion by two to three times compared to hard rock. The Indo-Gangetic plains, covered with thick layers of sediment, are particularly vulnerable to this amplification effect. Liquefaction, where saturated sandy soils lose strength and behave like liquid during shaking, poses an additional danger in coastal and riverine areas.

Building structures and construction quality 🔗

The design, materials, and construction quality of buildings are critical factors in determining earthquake damage. Old unreinforced masonry buildings, structures with heavy roofs, buildings with irregular shapes, and those with soft stories (ground floors with large openings for parking or shops) are particularly vulnerable. Poor construction practices such as using low-quality materials, inadequate reinforcement, and lack of proper connections between structural elements significantly increase damage risk.

Measures for earthquake preparedness 🔗

Building codes and standards 🔗

India has developed comprehensive earthquake-resistant design standards to minimize damage and loss of life. The Bureau of Indian Standards publishes IS 1893, which provides criteria for earthquake-resistant design of structures, and IS 4326, a code of practice for earthquake-resistant construction of buildings. These codes specify design forces, material requirements, and detailing practices based on seismic zones.

Key provisions include requirements for ductile detailing of reinforced concrete structures (IS 13920), guidelines for low-strength masonry buildings (IS 13828), and standards for industrial structures. The codes mandate adequate strength, stiffness, and ductility in buildings to withstand expected earthquake forces. Strict enforcement of these standards in high-risk zones is crucial for public safety.

Retrofitting and strengthening existing structures 🔗

Many existing buildings in earthquake-prone areas were constructed before modern seismic codes came into effect. Retrofitting guidelines (IS 13935) provide methods to strengthen these vulnerable structures through techniques such as adding shear walls, steel bracing, jacketing of columns, and base isolation. The National Disaster Management Authority conducts regular awareness campaigns and provides technical guidance for retrofitting programs.

Beyond individual buildings, creating earthquake-resilient communities requires proper urban planning, including maintaining adequate separation between structures, avoiding construction on unstable slopes, and protecting critical infrastructure such as hospitals, schools, and emergency services facilities. Regular earthquake drills, public awareness programs, and preparedness planning at community and institutional levels are equally important non-structural measures.

What do you think? How prepared is your community for earthquake risks? What steps can you take personally to ensure your home or workplace meets seismic safety standards?

References

1. https://www.pib.gov.in/PressReleasePage.aspx?PRID=1740656
2. https://en.wikipedia.org/wiki/Earthquake_zones_of_India
3. https://pubs.usgs.gov/gip/dynamic/understanding.html
4. https://www.pmfias.com/interaction-of-tectonic-plates-indian-plate/
5. https://nidm.gov.in/safety_earthquake.asp
6. https://bis.gov.in/other/quake.htm