An earthquake of magnitude 4.0 struck Delhi-NCR early Monday morning, causing strong tremors. Experts explain the reasons behind the intense shaking.
Early Monday morning, residents of Delhi-NCR and several parts of northern India experienced strong tremors, shaking high-rise buildings and prompting many to rush outdoors. The earthquake, measuring 4.0 on the Richter scale, struck at 5:36 AM IST. The National Centre for Seismology (NCS) reported that the epicenter was located within Delhi’s Dhaula Kuan.
While a 4.0-magnitude quake is considered moderate, its impact felt stronger due to its shallow depth and close proximity to densely populated areas. Earthquakes with epicenters within a city lead to more intense shaking because seismic waves travel a shorter distance before reaching structures, amplifying the tremors.
Why the Tremors Felt So Strong
Several factors contributed to the strong sensation of the earthquake:
- Epicenter within Delhi: The earthquake originated beneath the city, meaning seismic waves had less distance to travel, making the tremors feel more intense.
- Shallow depth: The earthquake’s shallow depth of 5 km contributed to the stronger shaking. Earthquakes closer to the Earth’s surface generate more intense shaking compared to deeper quakes of similar magnitude.
- Urban infrastructure: High-rise buildings in Delhi, Noida, and Ghaziabad sway more due to their height, amplifying the sensation of shaking.
- Soil composition: Soft alluvial soil in some areas of Delhi can amplify seismic waves, further intensifying the tremors.
Details from Seismologists
National Centre for Seismology Director OP Mishra explained that the earthquake’s shallow depth caused people to feel the effect more strongly. While the region has experienced earthquakes before, this one was notable for its proximity to the surface. Mishra noted that the earthquake was not related to plate tectonics but was instead due to local effects. An aftershock of around 1 or 1.2 magnitude is expected.
The location of the epicenter was Jheel Park in Dhaula Kuan. Mr. Modi urged people to stay alert for possible aftershocks and confirmed that authorities are closely monitoring the situation.
Delhi’s Seismic History
Delhi falls in Seismic Zone IV, making it prone to moderate-to-strong earthquakes. The city sits near active fault lines, including the Delhi-Hardwar Ridge and the Mahendragarh-Dehradun fault. The tremors were caused by tectonic plate movement along one of these fault lines, where stress builds up over time and is released as an earthquake.
Earthquake Intensity and Magnitude
The intensity of an earthquake is measured on the logarithmic Richter scale. Each whole-number increase represents a tenfold increase in the amplitude of seismic waves and about 32 times more energy release. For example, a magnitude 4.0 earthquake produces 10 times stronger shaking and releases 32 times more energy than a 3.0 earthquake. Similarly, a 5.0-magnitude earthquake shakes 10 times more than a 4.0 and releases 32 times more energy. By the time an earthquake reaches magnitude 6.0, the shaking is 1,000 times stronger than a 3.0, and the energy released is 32,000 times greater.
Past Seismic Events
Dhaula Kuan has been the epicenter of seismic activity before, including a 3.3 magnitude earthquake in 2015. Dr. OP Mishra mentioned that this was the most powerful earthquake to hit Dhaula Kuan since 2007, when it was the epicenter of a 4.7-magnitude quake.
Reactions and Response
Residents shared their experiences, with many expressing fear and noting the high magnitude of the earthquake. Delhi Police issued an emergency number for assistance, assuring residents of their safety. Just hours later, another 4.0 magnitude earthquake struck Siwan city in Bihar.
Earthquakes are occasionally felt in Delhi when they strike the nearby geological faultline where the Indian tectonic plate collides with the Eurasian plate, forming the Himalayas. Quakes centred on the Indian capital itself are relatively rare. This morning’s earthquake comes amid heightened seismic activity in the Himalayan region and a month after a powerful 7.1-magnitude temblor struck the foothills of the Himalayas near one of Tibet’s holiest cities, killing at least 126 people.
Sources: https://timesofindia.indiatimes.com/india/why-did-the-4-0-magnitude-earthquake-in-delhi-ncr-feel-so-strong/articleshow/118315557.cms
https://www.independent.co.uk/asia/india/earthquake-delhi-ncr-magnitude-modi-latest-b2699292.html
https://www.hindustantimes.com/india-news/delhi-earthquake-magnitude-4-why-did-delhi-ncr-feel-such-strong-tremors-today-ncs-epicentre-101739758016795.html