kolkata earthquake

 Introduction.

In the early hours of 25th February 2025, Kolkata experienced a significant seismic event that has reignited discussions about the city's vulnerability to earthquakes. At 6:10 AM, a 5.1 magnitude earthquake struck the Bay of Bengal, with tremors perceptible across Kolkata and its neighbouring regions. Residents reported feeling sudden jolts, leading to momentary panic, though no immediate damage or casualties were reported.

This recent Kolkata earthquake serves as a stark reminder of the city's inherent seismic risks. Situated atop the Eocene Hinge Zone, a fault line merely 4.5 km beneath the surface, Kolkata is susceptible to seismic activities. Experts have long cautioned that this dormant fault line could become active, potentially triggering earthquakes of magnitude 6 or higher. Such an event could have catastrophic consequences for the densely populated metropolis.

The city's geological composition further exacerbates its vulnerability. A comprehensive study by IIT Kharagpur revealed that Kolkata rests on a foundation of soft alluvial soil, comprising sand, clay, silt, and decomposed vegetation. This composition extends up to 7.5 km deep and includes shallow groundwater aquifers. In the event of a major earthquake, this soft soil is prone to liquefaction—a process where the ground temporarily loses its strength and behaves like a liquid. This phenomenon could cause buildings to sink or collapse, especially in areas like Salt Lake, Rajarhat–New Town, and parts of South Kolkata along the EM Bypass.

Adding to the concern is the structural integrity of many buildings within the city. Professor Debasish Bandyopadhyay of Jadavpur University has highlighted that numerous structures, particularly those exhibiting a tilt, are at heightened risk during a significant seismic event. The combination of Kolkata's soft soil and non-compliance with established construction norms has resulted in buildings that are ill-equipped to withstand substantial tremors. The professor emphasizes the necessity for deep foundations and strict adherence to construction standards to mitigate potential disasters.

Historically, Kolkata has not been immune to seismic disturbances. The 1934 Nepal-Bihar earthquake, with a magnitude of 8.1, had profound effects on the city. Several areas, including Metiabruz, Ballygunge, Rabindra Sadan, and Sovabazar, experienced significant damage due to soil liquefaction. This historical precedent underscores the potential devastation a major Kolkata earthquake could unleash.

In light of these risks, the city's preparedness for a major earthquake has come under scrutiny. The West Bengal Disaster Management Department has established crisis management protocols for natural calamities. However, experts advocate for a more robust approach, including the enforcement of stringent building codes, regular structural assessments, and public awareness campaigns. Retrofitting existing structures to comply with seismic standards is also deemed essential to enhance resilience against future Kolkata earthquakes.

The recent tremors have also sparked discussions about the safety of high-rise buildings in Kolkata. Earthquake expert Sujit Dasgupta has pointed out that resonance waves generated during seismic events can pose significant threats to tall structures, especially if they are not designed with seismic considerations in mind. Given Kolkata's proximity to Seismic Zone 5 regions, such as Nepal and North Bengal, there is a pressing need to evaluate and reinforce the city's high-rises to withstand potential earthquakes.

Public sentiment reflects a growing awareness and concern regarding these issues. Social media platforms were abuzz following the recent tremors, with residents sharing their experiences and expressing apprehension about the city's readiness for a more severe event. This collective consciousness underscores the importance of proactive measures to address the multifaceted challenges posed by Kolkata's seismic vulnerabilities.

In conclusion, the 25th February 2025 Kolkata earthquake has served as a critical reminder of the city's susceptibility to seismic events. The interplay of geological factors, structural vulnerabilities, and historical precedents necessitates a comprehensive and proactive approach to earthquake preparedness. By implementing stringent building regulations, enhancing public awareness, and investing in infrastructure resilience, Kolkata can better safeguard its residents against the inevitable forces of nature.