The earthquake zones in India are classified into four major types II, III, IV, and V, based on the intensity of seismic activity during earthquakes and past scientific data.
These zones are classified by a nodal agency called the National Center for Seismology, which is part of the Ministry of Earth Sciences.
In this article, we will understand India’s seismic zoning system, the nature of each seismic zone, and the major areas that fall under these zones.
Classification of Earthquake Zones in India – Sesmic Z
The four seismic zones of India are classified and established by the Bureau of Indian Standards (BIS) and periodically updated in the seismic zoning map IS:1893 (part 1).
Zone V exhibits the highest seismic activity out of the four zones, while Zone II has the lowest impact.
According to international standards, these zones differ on the MSK scale (Medvedev-Sponheuer-Karnik scale). This scale measures earthquake intensity, ranging from I to XII.
Additionally, level I on the MSK scale indicates hardly observable effects, while level XII signifies total destruction with extreme impact.
Considering the history of the earthquakes, the Ministry of Earth Sciences of India stated that 59% of the country’s land mass is prone to moderate to severe seismic activity.
Based on the analysis of seismic data and related scientific information, the earthquake zones in India are classified as follows.
Zone 5 – Very High Intensity and Very High Damage Rate
Out of the four earthquake zones in India, Zone 5 represents the highest seismic activity and can have the highest risk of damage.
This zone will have a magnitude of 7 or more on the Richter scale and experience intensities of IX and above on the MSK Scale.
The zone factor assigned to this zone is 0.36.
According to the Ministry of Earth Sciences, ~11% of the area of the country falls under the zone V category.
The zone V regions usually suffer the highest impact because these areas sit on the plate boundaries where high earthquake intensity occurs.
Some of the major earthquake incidents in India that have seen Zone 5 impact include
- Assam earthquake (1897) – 8.2 to 8.3 magnitude
- Bihar, Nepal Earthquake (1934) – 8.4 magnitude
- Uttarkashi earthquake (1991) – 6.8 magnitude
Areas falling under Zone 5 regions include
- Parts of Jammu and Kashmir
- The entire North-east Indian states
- Parts of Bihar (north and middle majorly)
- Rann of Kutch in Gujarat
- Andaman and Nicobar islands
Zone 4 – High Damage Risk
The Zone 4 region can cause severe damage to structures that are less stable or rigid. This zone experiences a magnitude of 6 to 7 on the Richter scale.
This zone falls under MSK Scale VIII. The IS code assigns a zone factor of 0.24 for zone 4
18% of the country falls under this category
Areas falling under Zone 4 regions include
- Parts of Northern India
- Parts of Jammu and Kashmir
- Northern Punjab
- Western Uttarpradesh
- A major part of Bihar state
- Northern region of Bengal and Sunderbans
Major cities under Zone 4
- Delhi
- Chandigarh
- Amritsar
- Patna
- Gorakhpur
- Gangtok
- Nainital
Zone 3 – Moderate Damage
The seismic activities in Zone 3 are classified as moderate. On the MSK Scale, they are categorized with an intensity rating of VII.
~ 30% of the country falls under the Zone III category. This zone typically have magnitudes ranging from 5 to 6 on the Richter scale.
a zone factor of 0.16 is assigned by IS code for zone 3 category
Areas falling under Zone 3 include
- Parts of Orissa, West Bengal and Tamilnadu
- Most of the Kerala state
Major cities under Zone 3
- Vijayawada
- Chennai
- Coimbatore
- Mumbai
- Pune
- Lucknow
- Vadodara
- Almost all Kerala cities
Zone 2 – Low seismic activity, Very Low Damage
Earthquake Zones in India falling under zone 2 signify a low intensity seismic activity, characterized by a reduced risk of significant damage.
These earthquakes typically result in only minor impacts on structures, making them less concerning compared to other zones.
The earthquake intensity of Zone 2 does not exceed a magnitude of 4.9 on the Richter scale.
This region is classified under the MSK scale with a rating of VI or lower. The IS code assigned a zone factor of 0.10 for this category.
Major cities under Zone 2
- Hyderabad
- Visakhapatnam
- Bangalore
- Nagpur
- Raipur
- Jaipur
- Gwalior
- Tiruchirappalli
- Madurai
