“A wave in the ocean”, “low growl” and that of a “cracker.”
That’s how residents described the sounds that accompanied tremors after a 4.0-magnitude earthquake hit India’s capital, Delhi and its surrounding areas at 5.36 am on Monday (February 17).
The
quake prompted Prime Minister Narendra Modi to issue a message, urging people to stay calm and be alert for “possible aftershocks. On X, he wrote that “authorities were keeping a close watch on the situation.”
This isn’t the first time that the capital has been shaken after it experienced tremors. Earlier on January 23, Delhi-NCR experienced strong tremors after a
7.2-magnitude earthquake hit Xinjiang in China, at a depth of 80 kilometres. This came after the capital experienced mild tremors on January 11, when a a 6.1-magnitude earthquake struck Afghanistan.
But what’s behind Delhi experiencing so many tremors? And just how bad was the quake this time around? We have the answers.
“Never felt earthquake like this in Delhi before. Even first floor was shaking,” said one person on X in the wee hours of Monday as a 4.0-magnitude earthquake struck Delhi, Noida, Greater Noida and Ghaziabad.
Experts state that the epicentre of the quake, which rocked the Delhi-NCR at 5.35 am, was near Durgabai Deshmukh College of Special Education in Dhaula Kuan and struck at a depth of five km. According to an expert, this region that has a lake nearby has been experiencing smaller, low-magnitude quakes once every two to three years. It recorded an earthquake of 3.3 magnitude in 2015, he told news agency PTI.
There has been no reports of injuries or damage, so far. However, residents were shocked and speechless following the quake. Some complained that the tremors were so intense that they “woke up for the first time without an alarm,” while others complained that “everything was shaking”.
One Delhiite said that the earthquake forced her out of bed while calling it “massive”. “You know it’s a massive one when it forces you out of your sleep and out of bed,” the user posted.
Many rushed out of their homes, questioning the strength of the tremors. As one wrote on X, “This was 4? It felt harder than 4.0 for sure. Or does it feel harder on the top floor?” Another added, “This is the first I’ve experienced that kind of tremor, my bed was literally shaking.”
A third also posted a video of a fan inside his home, and captioned it, “Earthquake in Delhi.”
Speaking to news agency ANI, a resident of Ghaziabad echoed similar feelings. “The tremors were so strong. I have never felt like this ever before. The entire building was shaking.”
Experts said that even though the quake was moderate, people felt it strongly because of its shallow depth and close proximity to densely populated areas. Earthquakes with epicentres within a city result in more intense shaking, since seismic waves travel a shorter distance before reaching structures, amplifying the tremors.
Dr OP Mishra, director, National Centre for Seismology (NCS) was quoted as saying, “Delhi has been experiencing minor earthquakes. This earthquake occurred in Dhaula Kuan. In 2007, an earthquake of 4.7 magnitude had occurred there. There is nothing to worry about. It is a seismic zone there… After 4.0 magnitude, the aftershock will be less by 1.2 magnitude, it is natural as it will heal it.”
Residents also complained of “hearing the tremors” for the first time. One netizen wrote that he “heard” the tremors for the first time. He posted, “This is the first time I “heard” an earthquake … what a shocker .. anyone else heard it too? Like a low growl ..(sic).”
Another user also spoke of a sound that she heard during the quake. On X, she wrote, “The fan did not move but the door, window and bed were shaking sideways, and there was a sound like a wave in the ocean. It was very scary, unlike any that I have experienced in the past. Hope it never happens again(sic),” she tweeted.
People present at New Delhi Railway Station also claimed that they heard loud noises as the tremors jolted the Delhi-NCR region. A passenger said he initially thought the sound was coming due to the movement of a train coach.
But what’s the reason for the rumbling? Scientists explain that shallow earthquakes are often coupled with sounds. The US Geological Survey explaining this phenomenon said that during quakes, the ground vibrates, creating short-period seismic wave motion that reaches the air and becomes sound waves. The first waves produced by an earthquake are P waves, which are like sound waves and can induce vibrations in the atmosphere.
The shallower the epicentre, the more energy that can reach the surface. High-frequency seismic waves pass through the ground, sometimes creating audible sounds.
Shortly after Delhi-NCR experienced the tremors, another quake was reported from Bihar’s Siwan as well as Odisha’s Puri. The National Centre for Seismology said that an earthquake of magnitude 4 on the Richter Scale struck Bihar’s Siwan with a depth of 10 kilometres.
As per reports, a 4.7-magnitude quake also hit Puri district in Odisha at 8.15 am.
Monday’s quake joins the long list of tremors and quakes that the
capital has experienced. In the last 100 years, about 25-30 earthquakes have already taken place in Delhi without significant damage.
In fact, Delhi has been categorised as a Zone IV region as per the Bureau of Indian Standards (BIS) seismic zoning map. Zone IV signifies a higher likelihood of experiencing earthquakes with moderate to high levels of intensity.
But what’s behind the frequent seismic activity in Delhi? Why does Delhi rattle so often? The answer lies in Delhi’s location. Experts note that the capital’s proximity to the Himalayan ranges makes it more susceptible to earthquakes and tremors.
The Himalayas were formed due to the continual collision of the Indian and Eurasian tectonic plates. This constant tectonic activity results in regular tremors, making the region an epicentre for recurring natural calamities like earthquakes and landslides.
Hence, Delhi, which is around 200-300 km away from the Himalayas frequently experiences seismic activity. As Professor Chandon Ghose of IIT-Jammu, an expert on earthquake engineering, explains: “Delhi is close to the Himalayas, which was formed by the mixing of tectonic plates such as India and Eurasia. Due to movements in these plates, areas like Delh-NCR, Kanpur and Lucknow, are most prone to earthquakes.”
Moreover, Delhi sits near three active seismic fault lines: the Sohna fault line, the Mathura fault line and the Delhi-Moradabad fault line.
Besides Delhi’s geographical factors, the construction in the capital contributes to its vulnerability. The Delhi-NCR region is dotted with high-rises, but few adhere to Bureau of Indian Standards norms.
And experts have stated that these high-rises would crumble in case of a significant earthquake in the region. A report on the “seismic hazard microzonation” of Delhi brought out by the Ministry of Earth Sciences, states that most places along the Yamuna and its flood plains, including the highly populated colonies of east Delhi, will be the worst hit if struck by a powerful earthquake. The Lutyens’ area, which houses the Parliament, central ministries and other important structures, also falls under the high-risk zone along with Delhi University’s north campus, Karol Bagh, Janakpuri, Paschim Vihar and Rohini. The Delhi airport and Haus Khaz fall under the second worst “high-risk category”.
It is hard to predict when Delhi will experience another quake, but seismic activity will continue in the capital for years to come.
With inputs from agencies
Link to article –
