An earthquake is a sudden shaking or trembling of the Earth’s surface caused by the movement of tectonic plates or volcanic activity thereby releasing energy. India is located in a seismically active region, and the country is prone to earthquakes with over 59 percent of India’s land area under threat of moderate to severe seismic hazards. Long-term and sustained efforts are required to address the problem of earthquake risk in India. The loss of life and property can be considerably minimised through maintaining better code compliance in prospective constructions and implementing seismic retrofitting on existing buildings, making them earthquake resilient.
Earthquake Vulnerability and Risk in India
India’s high earthquake risk and vulnerability are evident from the fact that about 59 percent of India’s land area could face moderate to severe earthquakes which means it is prone to shaking of MSK (Medvedev–Sponheuer–Karnik scale) Intensity VII and above.
- Tectonic sub-regions: India has three major tectonic sub-regions – the Himalayas to the north, the Ganges and other river plains, and the Peninsula.
- The entire Himalayan Region is considered to be vulnerable to high-intensity earthquakes of a magnitude exceeding 8.0 on the Richter Scale. This is due to the ongoing subduction of the Indian Plate under the Eurasian Plate.
- Shillong, 1897 (M 8.7); Kangra, 1905 (M.8.0); Bihar–Nepal, 1934 (M 8.3); and Assam–Tibet, 1950 (M 8.6) are some of the highly intense earthquake events.
- Scientists are aware of distinct gaps along the Himalayan axis where the previous release of geological stress does not entirely account for the strain that has accumulated.
- For example, the Central Himalayas have historically had fewer earthquakes than other locations. As a result, it is one place where a significant earthquake is likely to occur in the future.
- The tectonic features and characteristics of the Himalayas are prevalent in the alluvial plains of Indus, Ganga, and Brahmaputratoo, as the rocks lying below the alluvial plains are just extensions of the Himalayan ranges only. Thus this region is also quite prone to seismic activities.
- The peninsular region is also susceptible to earthquakes due to intra-plate faults and the internal deformation of the Indian Plate.
- Kachchh, Narmada–Son, and Godavari rifts, the Aravalli–Delhi Fold Belt is the site of noteworthy seismicity.
- The Bhadrachalam earthquake of April 13, 1969, and the Broach earthquake of March 23, 1970, are two major intraplate earthquakes associated with paleo rift zones in the stable continental region of peninsular India. The pre-existing faults get reactivated due to strain accumulation or fault weakening.
- The entire Himalayan Region is considered to be vulnerable to high-intensity earthquakes of a magnitude exceeding 8.0 on the Richter Scale. This is due to the ongoing subduction of the Indian Plate under the Eurasian Plate.
- Aggravated risk: The increase in earthquake risk is due to a spurt in developmental activities driven by rapid urbanisation, mining activities, rapid expansion of the infrastructure in moderate or high-risk areas, etc.
Earthquake Zones in India
The Bureau of Indian Standards (BIS) has divided India into four seismic zones based on the level of seismic hazard. Approximately 11% of the country is in zone V, 18% in zone IV, 30% in zone III, and the rest in zone II