What was the rumbling sound that accompanied Delhi earthquake?

Residents in Delhi experienced a magnitude 4 earthquake early Monday, with loud rumbling sounds accompanying.

Strong and powerful tremors jolted Delhi early Monday morning as an earthquake of magnitude four hit the national capital and surrounding areas at around 5:36 am. Accompanying strong tremors was a loud rumbling sound that several people reported hearing during the earthquake.

Strong tremors were felt across Delhi-NCR at around 5:36 am on Monday. (PTI)

People on social media reported waking up to violent shaking and a loud sound. A user on X said, “Most unsettling thing is it's possibly the first time I could also hear an earthquake. Usually it's the objects in the house shaking which makes a sound, but this time it was very clearly the earth.”

Sundar Lal, a resident of Delhi’s Sita Ram Bazar said that he initially mistook the noise for monkeys on the terrace, according to a PTI report.

"At first, we thought there were monkeys on our terrace making noise but then we realised it was an earthquake, so we all ran outside," he said.

Anil, a resident of Nehru Nagar, told PTI that he heard a loud sound when the tremors hit. "There was a loud sound and strong jolts. My wife and I were very scared. The first thing we did was pick up our daughter and rush outside," he said.

What was the sound

The epicenter of the earthquake on Monday morning was in Delhi’s Dhaula Kuan area and the depth of the quake was just 5 km, according to the National Centre for Seismology.

The answer to the booming sound might lie in the shallow depth of the earthquake.

According to the United States Geological Survey, small shallow earthquakes sometimes produce rumbling sounds or booms that can be heard by people who are very close to them. High-frequency vibrations from the shallow earthquake generate the booming sound, the USGS website says. However, when earthquakes are deeper, those vibrations never reach the surface.

Sometimes the earthquakes create booming sounds even when no vibrations are felt.

Why is Delhi so vulnerable to earthquakes

India has been divided into several zones which indicate the frequency of earthquakes in a particular region. Delhi is located in Zone IV which, according to the DDMA, has “fairly high seismicity”. This makes Delhi a “high-risk area” when it comes to earthquakes. Generally, the earthquakes in Delhi are of magnitude 5-6. However, an earthquake of magnitude 7-8 is an “occasional” occurrence in Delhi.

The Delhi-Haridwar ridge and Delhi-Moradabad fault are two major lineaments that pass through Delhi and make it more sensitive to earthquakes. Several other weak zones and faults are also near Delhi, such as the Mahendragarh-Dehradun subsurface fault, Moradabad fault, Sohna fault, great boundary fault, Delhi-Sargodha ridge, Yamuna River lineament, Ganga River lineament among others, according to the National Center for Seismology.

Delhi's proximity to the Himalayas, which are seismically very active, also makes it prone to tremors.