An earthquake of magnitude 4 struck New Delhi in the wee hours of February 17, 2025. The tremors originated at a shallow depth of 5 kilometres, according to the National Seismological Centre.
Shallow earthquakes occur at a depth between 0 and 70 km, intermediate earthquakes occur at 70-300 km and deep earthquakes at 300-700 km. Delhi often witnesses shallow earthquakes, said CP Rajendran, adjunct professor, School of Natural Sciences and Engineering, National Institute of Advance Studies, to Down To Earth.
Two factors could have driven this shallow earthquake. One is that Delhi is a high-risk area, falling in zone IV (fairly high seismicity where the general occurrence of earthquakes is of 5-6 magnitude). The seismicity around Delhi appears to be associated with a major geological structure, which is known as the Delhi-Hardwar Ridge passes through the territory.
The seismicity is due to the collision of the Indian plate with the Eurasian plate, which is happening for the last 50 million years. These colliding plates store energy. Earthquakes occur when a plate’s margin finally slip to release energy.
The second potential reason could be groundwater extraction. “Studies have shown that groundwater extraction could be a potential trigger. When there is less water, the pressure in the rocks is released, causing a quake,” explained Rajendran.
The low magnitude but moderate seismicity rate of Delhi region exhibits significant variation, both in short-term at annual seasonal scale and in long-term at decadal scale, a 2021 study published in the journal Scientific Reports suggested.
However, it correlates with the anthropogenic groundwater pumping for extensive irrigation, urban activities and seasonally controlled hydrological loading (related to changes in water storage), cycle of Indo-Ganga Basin-hosted freshwater aquifers.
Delhi is no stranger to earthquakes. The region has seen several moderate and strong earthquakes in 1720, 1831, 1956 and 1960 and multiple small magnitude earthquakes.
The 2021 paper noted that a majority of these earthquakes occur in the upper 25 km of the Earth’s crust, leading to shallow quakes.
The link between groundwater extraction and earthquakes was reported in other parts of the world as well. In 2013 and 2018, earthquake swarms with a magnitude of 4.5 occurred at roughly 5 km from the northern section of the Dead Sea Transform Fault.
A 2019 study published in the journal Geophysical Research Letters looked at aquifer pressure data and seismic monitoring to suggest that groundwater withdrawal triggered these earthquakes.
More recently, a 2023 paper published in the Bulletin of the Seismological Society of America also linked groundwater extraction to a December 2023 magnitude 6.8 earthquake in the High Atlas Mountains (Morocco). More studies are needed to study this link, explained Rajendran.
Shallow earthquakes are the more common kind. About 75 per cent of the total energy released from earthquakes is from shallow-focus ones, according to a blog post from the Open University.
Though large earthquakes originating at a depth of 50 km or more cause widespread damage, the intensity of shaking is reduced as the seismic waves travel at least 50km before they reach the surface.
Destructive earthquakes, however, are mostly shallow, concentrating in the upper crust of continents and the shallow portions on the megathrust, according to a 2024 study published in Earthquake Science. Shallow quakes become more destructive if their magnitudes are larger than 6, causing significant damages to the infrastructure and society.
But buildings in Delhi are vulnerable. The Bureau of Indian Standards developed its first code on seismic design in 1962. However, India lacks a legal framework to ensure all constructions in Delhi adhere to these provisions. “The results is that most buildings in Delhi may not meet codal requirements on seismic resistance. Moreover, even if from now on we somehow ensure that all new construction will be earthquake resistant, there still will remain a very large inventory of old buildings that will be deficient for seismic safety,” read the website of the Delhi Disaster Management Authority.