The tremors that people in the Delhi-NCR (National Capital Region) felt on Wednesday, when a minor earthquake of 3.2 magnitude on the Richter scale hit Noida, were the third such felt in just the past 5 days.
The National Centre of Seismology has recorded around 10 such earthquakes in and around Delhi-NCR between April 12 and May 29 in 2020.
The increasing frequency of the earthquakes has left residents worried, with social media messages doing the rounds that there could be “a big one around the corner”.
An earthquake is imminent in the Himalayan foothills, said C.P. Rajendran, a professor at the geodynamic unit of the Jawaharlal Nehru Centre for Advanced Scientific Research in Bengaluru, but added that one could not ascertain exactly when it was going to happen.
A study that Rajendran led in 2018 had found that an earthquake which took place some time between the years 1315 and 1440 CE unzipped a stretch of about 600 km, the length of the seismic gap stretching from Bhatpur in India to beyond Mohana Khola in Nepal in the central Himalayas.
A seismic gap is a part of an active fault that has experienced little or no seismic activity for a long period.
The region, the study found, had remained seismically quiet for 600-700 years, creating an “enormous stacking up of seismic strain”, which could result in an earthquake of a magnitude of 8.5 or more at any time in the near future.
This, the study said, could affect the foothills of the Himalayas and the northern plains of India, including cities such as Delhi.
In an interview with HuffPost India over email, Rajendran explained why there have been minor earthquakes in Delhi over the past few weeks, the impact of a massive earthquake in Delhi and the steps the government needs to take to prepare for this.
Excerpts from the interview:
Delhi has experienced several minor earthquakes in the last few months. Can you explain to us why this has happened?
Delhi holds many faults associated with several major 100s of km-long deeper transverse linear geological structures perpendicular to the Himalayan mountain axis. Some of the main structures are called Delhi-Haridwar Ridge, Delhi-Sargodha Ridge and Great Boundary Fault. There are many active faults associated with these structures. As they are located close to the Himalayan tectonic regime the rocks within fault zones periodically accumulate stress due to the continuous northward movement of the Indian continental plate under the Himalayan mountain. The stresses get released variously along these faults that produce earthquakes of various sizes (moderate and smaller sizes). The May 29 earthquake in Rohtak, near Delhi, was 4.6 magnitude.
Delhi and its neighbourhood had seen similar earthquakes in the past. In 1960, Delhi shook with 4.8 magnitude, greater than what happened on May 29. About 75% of the buildings around the epicentre of the 1960 shock — between Northern Cantt. and Gurgaon — developed cracks, and minor damage to Red Fort and Rashtrapati Bhavan was also reported. About 100 people were injured by falling debris and in stampedes. The faults around Delhi can generate earthquakes up to 6.5 magnitude. In 1720, another damaging earthquake occurred in Delhi. In 1966, an earthquake of 5.2 magnitude near Moradabad.
Some geologists have said that Delhi may see a major earthquake in the future. Is this true?
A major earthquake from the Central Himalayan foothills is expected. The studies suggest that this part of the Himalaya has not seen a major earthquake (greater than 8 magnitude) for hundreds of years unlike other parts of the Himalaya. The science tells us that the stresses due to the northward movement of the Indian plate piled up enormously there and it has to be released through a major earthquake or a series of earthquakes. We can only say it is imminent but cannot say when this is going to happen.
Are specific parts of Delhi more at risk from earthquakes. If so, why?
The areas around Yamuna River are more vulnerable because high soil thickness amplify the seismic energy and generate more damage to buildings. For that matter, the entire alluvial plain along the Ganga river is highly vulnerable to a major earthquake from the Himalaya.
A study you conducted showed the Himalayan foothills are in danger of an imminent earthquake. What parts of India did you find could be affected by it? And how soon could it happen?
Parts of Delhi, Haryana and the UP will be affected, other than parts of the central Himalaya (the Garhwal and Kumaun parts). It could happen anytime.
What impact could it have on Delhi? Is Delhi as a city prepared to cope with a massive earthquake? If not, why?
Delhi lies in ‘seismic zone IV’ or an area of high damage risk from earthquakes. Delhi will be heavily damaged. It is pointed out by architects that 95% of the buildings in Delhi do not follow the safety code. Delhi’s population has also grown many times in the last 70 years. If a 1720-like earthquake recurs, the loss to life and property could be colossal in today’s Delhi. The destruction to property and lives would be colossal from a massive earthquake from the central Himalaya.
What are the steps the government needs to take immediately so that Delhi can cope with a massive earthquake?
The seismic ground motions from an earthquake will have variable characteristics depending upon the soil and site conditions. The microzonation conducted by the Ministry of Earth Sciences in Delhi tell us that can broadly be divided into various land units with matching hazard potential.
Most of the area along the Yamuna flood plains, parts of north Delhi and southwest Delhi constitute zones of higher seismic hazard whereas the central part and the ridge form lower hazard zones than rest of Delhi.
Most of the lives lost in an earthquake are due to collapse of non-earthquake resistant buildings. So, answer is simple — follow already available building rules strictly and right construction practices, but the rules are always flouted and right construction practices.
Also, the government should take steps to strengthen the historical monuments in Delhi and its neighbourhood (like Taj Mahal). In 1803, an earthquake of magnitude 7.5 had damaged Qutab Minar.
Are there countries that have been able to prepare themselves successfully to deal with earthquakes that India can learn from?
The US, Japan and Taiwan. They are better prepared in terms of early warning systems and collection of high-quality data through greater funding for earthquake research and also more adept at using engineering principles in earthquake prone areas for making earthquake resistant structures, as suggested by the scientists.
Editor’s note: This headline has been changed to reflect the expert’s views more accurately.