Seismologists call this pattern of quakes an earthquake swarm, and Maharashtra has experienced them often before. Of the 29 tremors during this period, 24 were in and around Nashik, four were in Palghar and one was in Nagpur. They weren’t particularly strong — the strongest was in Nagpur on August 8, of magnitude 4.3 — although they were also shallow, around 5-8 km deep.
There has been a spate of small earthquakes in Maharashtra over the last fortnight, according to local reports.
In Koyna in Maharashtra, in fact, researchers have been following earthquakes that have been occurring for decades around the Koyna-Warna reservoir, in a famous case of reservoir-triggered seismicity . Researchers who studied the Palghar swarm in 2018 using satellite data found evidence of land subsidence and suggested that rainwater moving into the subsurface region could have triggered the faults. A more detailed study that analysed data of more than 21,000 earthquakes between January 2019 and October 2020 in Palghar concluded that seismic activity had increased following rainfall and that water had migrated into cracks and fissures, increasing pore pressure and helping drive the swarm. As scientists from the CSIR-National Geophysical Research Institute, Hyderabad, and the Academy of Scientific and Innovative Research, Ghaziabad, wrote in a 2025 paper in Scientific Reports :
