National Center for Seismology said the earthquake struck at a focal depth of five kilometres in Delhi-NCR on February 17, 2025
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Strong tremors were felt in the national capital and adjoining regions as an earthquake of 4.0 magnitude struck the region early on Monday (February 17, 2025). The National Center for Seismology said the earthquake struck at a focal depth of five kilometres at 5:36 am.
After Delhi, NCR, tremor felt in Bihar also at 4.0 magnitude. The National Center for Seismology said the earthquake struck at a depth of 10 kilometres at 8:02 am.
Shallow earthquakes, originating five or 10 kilometres below the surface, tend to cause more damage than those originating deep below the surface.
Shallow earthquakes are between 0 to 70 km deep; intermediate earthquakes, 70 to 300 km deep; and deep earthquakes, 300 to 700 km deep.
An instance of the devastating effect of a shallow earthquake would be the 5.6 magnitude earthquake in Indonesia in Novermber 2022 that left more than 160 dead and hundreds injured as buildings crumbled and terrified residents ran for their lives on the main island of Java.
According to the U.S. Geological Survey, “There is not one magnitude above which damage will occur. It depends on other variables, such as the distance from the earthquake, what type of soil you are on, building construction” and other factors.
Why an earthquake’s depth matters?
A quake’s destructive force depends not only on its strength, but also on location, distance from the epicentre and depth.
Quakes can strike near the surface or deep within the Earth. Most quakes occur at shallow depths, according to the U.S. Geological Survey.
Shallow quakes generally tend to be more damaging than deeper quakes. Seismic waves from deep quakes have to travel farther to the surface, losing energy along the way.
Shaking is more intense from quakes that hit close to the surface like setting off “a bomb directly under a city,” said Susan Hough, a USGS seismologist.
Commenting on the tremor felt in Delhi-NCR region, National Centre for Seismology Director OP Mishra says, “Seismologically, it is not new region, earthquakes have happened earlier in the region. Earlier, there was 4.6 magnitude earthquake in 6 km periphery, but it was deeper, with 10 km depth. There is a difference. It was not a plate tectonic earthquake, it was due to in situ material heterogeneity, it was due to local effect. We can expect aftershock of around 1 or 1.2 magnitude.”
Published – February 17, 2025 10:26 am IST
