Context: 

Recently, An earthquake of magnitude 4.0 occurred at 05:36 IST, in New Delhi, whose epicenter is at 28.59°N and 77.16°E at a shallow depth of 5 km.

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The earthquake is widely felt in the Delhi-NCR region and neighboring states.

There are two reasons why this earthquake felt particularly strong:

• The National Center for Seismology said the earthquake struck at a focal depth of five kilometers.
• The epicenter was located well within Delhi, 10 km from red Fort in South West Direction.

After Delhi NCR, tremors felt in Bihar also at 4.0 magnitude. The National Center for Seismology said the earthquake struck at a depth of 10 kilometers at 8:02 am.

The city lies in Seismic Zone 4, where earthquakes of magnitude 5 to 6 are fairly common and the region’s seismic activity is linked to the ongoing collision between the Indian and Eurasian plates, which has been occurring for over 50 million years.

However according to the National Centre for Seismology Director, it was not a plate tectonic earthquake, it was due to in situ material heterogeneity, it was due to local effects.

Earthquake

An Earthquake is a sudden, rapid shaking of the earth caused by the breaking and shifting of rocks beneath the earth's surface

It occurs when two blocks of the earth suddenly slip past one another. The surface where they slip is called the fault or fault plane.

Hypocenter/focus: It is the location below the earth’s surface where the earthquake occurs.

Epicenter: It is the location directly above it on the surface of the earth. 

Earthquakes are recorded by instruments called seismographs. The recording they make is called a seismogram.

An earthquake’s destructive force depends not only on its strength but also on location, distance from the epicenter, and depth. Shallow quakes generally tend to be more damaging than deeper quakes.

The earthquakes are divided into the following three zones based on depth of focus: 

• Shallow earthquakes have a focus 0 – 70 km deep.
• Intermediate earthquakes have a focus 70 – 300 km deep.
• Deep earthquakes have a focus 300 – 700 km deep.