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Mint Primer | How vulnerable is north India to earthquakes?
Summary
- In 2019, the NDMA published the Edri report, analysing the risk to 50 cities. Delhi and 29 other cities fall in the medium-risk category. However, 13 cities—mostly Himalayan ones, but also cities like Vijayawada or Maharashtra’s Ratnagiri—fall in the high-risk category.
An earthquake measuring 4.0 on the Richter Scale jolted New Delhi at dawn on Monday, causing widespread alarm. A few hours later, another earthquake of similar strength hit Bihar’s Siwan. Should we be worried? Mint explains.
What are the most dangerous quakes?
The edge of the Indian plate that’s pushing into Asia lies deep under the Himalaya, along a fault called the Main Himalayan Thrust (MHT). This is where the truly big earthquakes occur. The MHT’s three shallower branches are close to most north Indian cities, including Delhi. Most monster earthquakes of between moment magnitude (Mw) 7.5 (Kashmir, 2005) and Mw8.4 (Nepal-Bihar, 1934) have occurred in these faults. Massive quakes can cause fissures along the ground and liquefy the soft alluvial plains of north India. Seismologists are of the view that at least one major quake, probably more, is overdue in the region.
What do we know about Delhi tremors?
At 5:36 am on Monday, an earthquake of Mw4.0 struck New Delhi. Despite being low in magnitude, it caused widespread alarm due to aggressive shaking and a loud noise coming from the ground. The National Centre for Seismology (NCS) said the epicentre was located 5km under Dhaula Kuan’s Jheel Park in central Delhi. The NCS director O.P. Mishra said the intensity was caused by the fact that it occurred at a shallow depth. He said this was not due to plate tectonics, but due to local geological reasons. The Dhaula Kuan area is located in the Delhi Ridge region, an extension of the Aravallis.
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Is there any cause for worry in Delhi-NCR?
Not immediately. The NCS said that there is a likelihood of much smaller aftershocks. Still, Delhi is at high risk from earthquakes. It is situated near two important fault lines (Delhi-Haridwar Ridge and Mahendragarh-Dehradun fault). But the greater risk is due to its close proximity to the edge of the Indian tectonic plate that’s pushing up into and under Asia.
What does NDMA say on India’s quake risk?
In 2019, the National Disaster Management Authority (NDMA) published the Earthquake Disaster Risk Index (Edri) report, analysing the risk to 50 cities. Delhi and 29 other cities fall in the medium-risk category. However, 13 cities—mostly Himalayan ones, but also cities like Vijayawada or Maharashtra’s Ratnagiri—fall in the high-risk category. While the report takes a comprehensive look at the architectural, planning and structural reasons underpinning the risk, no further work has been done in the following six years.
Are Indian cities prepared for quakes?
Quite simply, no. Cities in the most vulnerable regions—the Indo-Gangetic plains, the Himalayan region and the Brahmaputra Valley—are already overbuilt. Cities like Delhi are a combination of self-constructed structures, slum clusters, resettlement colonies, unauthorized colonies, urban villages and regularized unauthorized colonies. Most earthquake guidelines, like NDMA’s do’s and don’ts, are therefore all about keeping casualties low, and ensuring “safe failure" of buildings.
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