Maharashtra has witnessed a series of low-intensity earthquakes over the past two weeks, with tremors reported mainly from Nashik and Palghar districts. Experts have described the repeated seismic activity as an “earthquake swarm.” As many as 29 tremors were recorded across the state between July 30 and August 14.
Of the 29 earthquakes, 24 were reported in Nashik, four in Palghar and one in Nagpur. Their magnitude ranged from 2.0 to 4.3 on the Richter scale, with the epicentres located around 5 to 8 km below the surface.
The strongest tremor occurred in Nashik on August 8, measuring 4.3 magnitude at a depth of around 5 km. Nashik also recorded six tremors on August 6, followed by four each on August 8 and August 10.
What Is an Earthquake Swarm?
An earthquake swarm refers to a sequence of small earthquakes occurring repeatedly in the same region over a relatively short period. It is different from an aftershock sequence, where smaller tremors follow a larger main earthquake.
In an earthquake swarm, there is usually no single major earthquake that can clearly be identified as the main event. Instead, several low-magnitude tremors occur in succession.
Why Is Nashik Experiencing Repeated Tremors?
According to IIT Bombay earthquake expert Professor Dipankar Chowdhury, such seismic activity can become more common during the monsoon. Nashik lies in the Deccan Plateau, where underground rock formations contain small cracks. Rainwater entering these fractures can increase underground pressure and trigger minor seismic movements.
This phenomenon, linked to groundwater pressure, is known as hydro-seismicity.
Similar earthquake activity has been reported in the region in the past, including in Palghar in 2023 and 2019.
Is Mumbai at Risk?
Experts say the current low-intensity tremors do not necessarily indicate an imminent major earthquake in Mumbai. Since the recent epicentres are relatively shallow, the energy is unlikely to travel very far.
However, experts stress the importance of earthquake-resistant buildings and stronger infrastructure to reduce potential damage from any major earthquake in the future.