'Shaken, sound like wave in ocean': Why did 4.0-magnitude earthquake in Delhi-NCR feel so strong?

synopsis

An earthquake measuring 4.0 on the Richter scale hit Delhi-NCR early Monday (Feb 17) at a depth of 5 km, according to the National Center for Seismology (NCS). The strong tremors were felt at  5:36 am. The sudden jolts shook homes, and high-rise buildings alike, prompting residents to rush outdoors in panic.

Though a 4.0-magnitude earthquake is considered moderate, its impact felt stronger than usual because of its shallow depth and close proximity to densely populated areas.

"Earthquake of Magnitude:4.0, Occurred on 17-02-24, 5:36 AM  IST, Lat:  28.59°N & Long :77.16°E, Depth: 5 Km, Location: 9km E of New Delhi," NCS posted on X.

Delhi shaken & stirred: Why did 4.0-magnitude earthquake feel so strong?

Earthquakes with epicentres within a city result in more intense shaking since seismic waves travel a shorter distance before reaching structures, amplifying the tremors. Delhi, which falls in Seismic Zone IV, is prone to moderate-to-strong earthquakes, making localised tremors more pronounced as the.

Experts noted that buildings, particularly high-rises, sway more due to their design, increasing the perceived intensity of shaking.

Epicenter within Delhi

Unlike quakes originating far away, this earthquake had its epicenter directly beneath the city. With the seismic waves having less distance to travel, the impact was immediate and forceful, amplifying the sensation of shaking.

Shallow Depth

The quake struck at a relatively shallow depth, which is a key factor in determining its intensity. Shallow earthquakes tend to generate stronger ground motion compared to deeper quakes of similar magnitude, making them feel much more severe on the surface.

Urban Infrastructure

Delhi, Noida, and Ghaziabad are home to towering high-rises, which naturally sway when the ground moves. This swaying effect, a result of the buildings' height and structural dynamics, made the tremors feel more pronounced, especially for those in multi-story buildings.

Soil Composition

Delhi's soft alluvial soil played a crucial role in intensifying the tremors. Loose, unconsolidated soil tends to amplify seismic waves, making the shaking feel even more violent in certain areas.

Delhi earthquake: PM urges to stay calm & alert for possible aftershocks

Prime Minister Narendra Modi urged the people of Delhi to stay calm and follow safety precautions after the jolts. 

"Tremors were felt in Delhi and nearby areas. Urging everyone to stay calm and follow safety precautions, staying alert for possible aftershocks. Authorities are keeping a close watch on the situation," PM Modi wrote on X (formerly Twitter).

No major damage or casualties have been reported, however, seismologists continue to monitor aftershocks and have advised citizens to stay informed about earthquake preparedness measures.