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Delhi NCR along with entire northern region of India is vulnerable to high seismic activity
Delhi, the capital of India, is not only the hub of governmental and business activities but also one of the most densely populated cities in the world. Delhi lies in the Seismic zone IV (four) which is classified as the high-damage risk zone incase of earthquakes. Over the years, Delhi has witnessed multiple earthquakes raising concerns over it’s geological placement and instability along with preparedness to withstand and counter seismic activities.
Seismic Zone Classification of India
India is divided into four seismic zones based on earthquake risks: Zone II, Zone III, Zone IV, and Zone V (Zone I was removed due to its negligible seismic activity). Delhi falls under Seismic Zone IV, which is classified as a high-damage risk zone.
High damage risk zone means that there is a potential of earthquakes of magnitude 6.0–7.5 or higher on the Richter scale. Peak ground acceleration (PGA) is the measure of maximum acceleration of the ground during an earthquake. PGA value between 0.2g and 0.8g can cause moderate damage. In seismic zone 4, the ground acceleration can range between 0.24g to 0.48g. Delhi NCR region is highly urbanised with dense population and infrastructure prone to high risk of damage and loss of life.
Delhi’s Proximity to Active Fault Lines
Delhi is located near several major fault lines that make it susceptible to seismic activities. Mahendragarh-Dehradun Fault line runs across the Delhi region. Moradabad Fault line is located towards the east of Delhi. Mathura Fault line extends towards the south. Delhi-Hardwar Ridge is a seismically active belt.
The Himalayan seismic belt, which is one of the most active earthquake zones in the world is about 200–300 km from Delhi. The continuous movement of the Indian tectonic plate under the Eurasian plate generates high seismic energy and scientists claim that there is immense accumulated energy and stress in the area. This accumulated stress could trigger major earthquakes that might affect Delhi and entire northern Indian region with devastating effects.
Local Soil Conditions Affect the Extent of Damage During Earthquakes
Certain areas of Delhi especially those along the Yamuna floodplains have soft alluvial soil that amplifies the seismic waves. With the amplifies waves the intensity of shaking during an earthquake also increases. Regions with loose soil and reclaimed land are more prone to liquefaction of soil causing severe infrastructure damage.
Historical Earthquakes in Delhi NCR Region
Delhi has experienced several earthquakes in the past, some of which were felt strongly due to nearby seismic activity:
- Year 1960 – Delhi experienced an earthquake of magnitude 6.0 which was strongest in the history of Delhi. The Epicentre was between Gurgaon and Delhi Cantt which led to minor injuries and structural damage in the Delhi NCR region.
- Year 1994 – An earthquake of magnitude 5 was registered on Ritcher Scale with the epicentre 280 Kms from Delhi.
- Multiple earthquakes of magnitude around 4 felt between since 2001 with frequency of occurrence increasing since Year 2020.
Earthquake Preparedness is Important
Delhi is a highly urbanized city with a mix of modern skyscrapers and old civic and historically relevant buildings. Even though Delhi NCR has seen rapid development over the past years, many buildings do not follow earthquake-resistant design principals. Older high rises may not withstand a strong earthquake. There are many old bridges and overpasses which require retrofitting to enhance seismic resilience. It is not just the infrastructure that is at risk but dense population increases the chances of loss of human lives as well as makes evacuation and rescue operations challenging incase of a calamity.
Delhi NCR being a high risk zone requires earthquake preparedness and rescue protocols in place. The Indian government has put some measures in place encouraging preparedness. For example, National Building Code (NBC 2016) mandates earthquake-resistant designs of new construction and retrofitting of older buildings. It is also mandated that retrofitting of critical infrastructure like hospitals, schools and government buildings must be done / improved. Government also mandates regular earthquake drills in schools, IT parks and other public places to check preparedness of the same.