IIT Kharagpur research shows rising seismic risk in the Bay of Bengal

The Indian Institute of Technology (IIT) Kharagpur has conducted a study revealing a rising seismic risk in the Bay of Bengal. Historically, the region was considered low-to-moderate for earthquakes, but new research suggests this perception is changing. On February 25, 2025, a magnitude 5.3 earthquake hit deep beneath the Bay's waters, shaking Kolkata and Bhubaneswar despite its relatively mild intensity.

This event prompted scientists to reassess their understanding of the area's seismic potential. Their investigation revealed that the Bay of Bengal is developing into a region capable of producing large-scale earthquakes due to shifting tectonic plates, sediment buildup from rivers, and the reopening of ancient ocean floor fractures.

Over the past century, the Bay recorded approximately 120 earthquakes, including several above magnitude 6.0. The researchers focused on intraplate earthquakes, those occurring within the Earth's crust rather than at plate boundaries. They discovered that the central Indian plate beneath the Bay is under immense stress due to the slow movement of the Indian tectonic plate.

This stress is not evenly distributed, and the deep offshore region is becoming increasingly prone to moderate-to-strong earthquakes that could endanger millions of people living along the coast. Using a statistical tool called the b-value, the researchers measured stress levels in the Earth's crust. High b-values indicate low stress with many small earthquakes, while low b-values suggest high stress that could lead to significant seismic activity.

The study found that offshore regions had b-values as low as 0.72, signaling significant strain on the deep-sea floor. The study attributes this stress largely to sediment loading from rivers like the Ganges and Brahmaputra, which have deposited massive amounts of sediment (up to 13 kilometers deep) on the oceanic crust. The combined effects of tectonic plate movement, sediment pressure, and ancient fractures have created a dynamic environment where deep-seated fractures could reactivate, triggering powerful earthquakes.

The research provides a new perspective on the Bay of Bengal as an evolving seismic hotspot, highlighting the need for updated disaster preparedness strategies. Coastal cities previously considered low-risk, such as Kolkata, may need to reassess their building codes and infrastructure resilience to mitigate potential intraplate threats from the ocean.