List of Earthquake Seismic Zones in India

An earthquake is simply a rapid vibration of the earth’s surface which arises due to the movement of the rocks (commonly called ‘plates’) under the surface of the earth. This happens due to elastic or isostatic adjustment attained by these rocks as a result of a human or natural activity. These vibrations may be as small as even unnoticeable to as strong and destructive enough to make buildings collapse down. As we all are aware that India, these days, is witnessing frequent tremors of earthquakes mainly in the Delhi-NCR and neighbouring regions. Indian cities, particularly towards the north & those which are closer to the Himalayas, have recorded bigger threats in the past. The Delhi-NCR belt and the regions adjacent to the Yamuna river etc., also fall under high-risk zones.

The point at which the seismic waves originate is called the focus. The focus lies below the earth’s surface. The point perpendicularly just above the focus is known as the ‘epicentre’. The earthquake is the first (and strongest) observed at the epicentre. The strength of the originated seismic waves is defined by the ‘elastic energy, which is the energy that is dissipated from the focus. 

(Image will be uploaded soon)

Image: The Earthquake Anatomy

Seismic Zones of India

Indian landmark has been classified into four seismic zones of India (often called ‘earthquake zones in India’). These are termed as zones II, III, IV and V. In this classification, zone V consists of the ‘very severe intensity zone’ (most seismic prone regions), zone IV is the ‘severe intensity zone’, zone III is the ‘moderate-intensity zone’ and zone II is the ‘low-intensity zone’ (least seismic prone).

(Image will be uploaded soon)

Image: Location of earthquake zones in India

List of Earthquake Zones in India

The variations in the geological situations of various regions imply variations in the likelihood of damages that could be caused by earthquake prone areas in India. Thus, it becomes necessary to draft the seismic zone map in order to identify these regions. Based on the intensities sustained during past damaging earthquakes, the 1970 version of the seismic zone map had five subdivisions of earthquake zones in India; zones-I, II, III, IV and V. The maximum Modified Mercalli (MM) intensity of seismic vibrations expected in these zones were V or less, VI, VII, VIII, and IX and higher, respectively. The map of the earthquake zone in India has been revised again in 2002. The earthquake prone areas in India are marked on the map. Now the number of seismic zones was reduced to four divisions; zones-II, III, IV and V. Also, the seismic zone map in the Peninsular regions was redistributed. Since this revision of the map, Madras comes under zone-III as against Zone-II in the older 1970 version of the seismic zone map.

• Zone-V (most earthquake prone areas in India):

This zone contains mostly the northeastern part of the country. It includes Jammu and Kashmir,  Uttarakhand, Himachal Pradesh, Rann of Kutch of Gujarat, North Bihar and Andaman and Nicobar islands.

• Zone-IV:

The parts of Jammu and Kashmir, Himachal Pradesh, Delhi, Sikkim, northern parts of Uttar Pradesh, Bihar and West Bengal, parts of Gujarat and small portions of Maharashtra near the west coast and Rajasthan.

• Zone-III:

• This zone comprises Kerala, Goa, Lakshadweep, remaining parts of Uttar Pradesh, Gujarat, and West Bengal, parts of Punjab, Rajasthan, Madhya Pradesh, Bihar, Jharkhand, Chhattisgarh, Maharashtra, Orissa, Andhra Pradesh, Telangana, Tamilnadu and Karnataka.

• Zone-II (least earthquake prone areas in India):

The zone covers the remaining parts of the country.

The list of earthquake-prone areas in India is given below.

Distribution of Earthquakes in India

The seismic zones of India are mostly distributed over the areas of Kashmir, the Western and Central Himalayas, Bihar, the North-East Indian region, the Rann of Kutch of Gujrat state and the Andaman and Nicobar islands.

(Image will be uploaded soon)

Image: India Earthquake Zone Map

Prominent Past Earthquakes in India

Over the past century, India witnessed a number of significant earthquake tremors frequently in some regions. Many of them took place in urban and populated areas leading to huge losses of lives and property while others went unnoticed due to the reasons that they either occurred deep inside the earth’s crust or they originated too far from the inhabited regions and hence were weak enough to even not get noticed by anyone.

Earthquakes in India, mostly occur in the Himalayan plate boundary (interplate-earthquakes). But some of them also occurred in the Peninsular region (intraplate earthquakes). In the 53 years from 1897 to 1950, four great earthquakes took place with M>8. Later in January 2001, another earthquake with similar strength of M7.7 was encountered at Bhuj.

These past earthquakes caused disasters but their experiences took the attention of the geologists and researchers to learn more about them and this led to the advancement of earthquake engineering. For instance, the 1819 Cutch earthquake produced an

unprecedented uplift of the ground of about 3m height over 100km (called Allah Bund). The 1897 Assam earthquake brought huge destruction over 500km radial range. The type of damage sustained led to the extension of the intensity scale from I-X to I-XII. The 1934 Bihar-Nepal earthquake caused extensive liquefaction of the ground over a distance of 300km (called the Slump Belt) in which many structures were damaged and went afloat.

Did You Know?

• Before a region is hit by an earthquake, the concentration of Radon gas usually increases in the atmosphere in that region. The rise in the amount of Radon gas indicates that the seismic waves might hit the region soon. Various studies have been done which suggest that the elevated amount of Radon gas in soil and groundwater may be the sign of an upcoming earthquake.

• The intensity (or strength) of an earthquake is measured using an instrument called ‘Seismograph’ which is sensitive to the vibrations that occur when a tremor strikes. It is helpful in providing valuable information regarding the earthquake such as the intensity (measured in various scales like Rossi-Forel scale, Mercalli scale, and Richter scale), duration of the vibrations etc.