What are aftershocks: How big a danger are these that PM Modi warned about after the earthquake in Delhi-NCR?

The earthquake tremors felt around Delhi and the National Capital Region (NCR) on Monday morning have created panic among the people. The intensity of the earthquake that occurred at around 5.36 am was measured at 4.0 on the Richter scale. However, the impact of the tremors recorded was quite strong.

After these earthquake tremors felt in Delhi-NCR, Prime Minister Narendra Modi also urged people to be cautious. The PM said in a post on X that earthquake tremors were felt in Delhi and surrounding areas. Everyone is urged to remain calm follow safety precautions and be alert to possible aftershocks. Officials are keeping a close watch on the situation.

In such a situation, it is important to know that despite the earthquake intensity being recorded low in Delhi, why was its impact so strong? When have such earthquake tremors been felt before? What are the aftershocks about which Prime Minister Narendra Modi has warned the public? Why are tremors felt one after the other 24-48 hours after a severe earthquake? Let's find out...

Why were strong tremors felt in Delhi despite a low-intensity earthquake?

After the earthquake in Delhi, according to the National Center for Seismology (NCS), the organization that keeps records of earthquakes under the Ministry of Earth Sciences of the Government of India, the intensity of the tremors was measured at 4.0. In such a situation, the question arises why was the tremor so strong despite such a low intensity? NCS director OP Mishra has answered this. He said that one of the reasons for this was that the epicenter of the earthquake was about five kilometers below the surface of the earth in Delhi itself, due to which the effect of the tremor on the earth was quite strong.

Mishra said that such shallow (coming from a depth of 5 to 10 kilometers in the ground) earthquakes cause more damage. Due to proximity to the surface, mild earthquakes are usually felt more intense than deep earthquakes. The recent earthquake was recorded five kilometers below the ground in Delhi's Dhaula Kuan area.

When have such earthquake tremors been felt in Delhi before?

According to records, such earthquake tremors have been felt many times before in Delhi-NCR. The geographical location of Delhi-NCR makes it vulnerable to earthquakes. This area is located in Seismic Zone-IV. Due to the presence of active fault lines in the area, mild earthquakes keep occurring from time to time. This area is included in the second most dangerous category in terms of earthquakes. However, till now most of the earthquake tremors have been minor and have not caused serious damage.

What are the aftershocks that PM Modi warned about?

After an earthquake, there are often many tremors, which continue for hours or several days. These tremors further increase the damage caused by the earthquake. According to the US Geological Survey, tremors are a sequence of earthquakes that come after a major earthquake on a fault. Tremors occur near fault lines (where there are holes between rocks). Though the tremors are weaker than the main earthquake, they can cause extensive damage.

Sometimes when the intensity of the main earthquake is high, its aftershocks are also strong and these tremors create obstacles in relief and rescue operations. Sometimes even rescue workers get caught in it.