Chandigarh's earthquake risk amplified by ground conditions, study warns

A recent scientific study has highlighted that Chandigarh and its surrounding areas face an increased risk of amplified earthquake shaking due to local ground conditions. Published in the Journal of Applied Geophysics, the research, conducted by scientists from the Central University of Himachal Pradesh, employed advanced geophysical and geotechnical investigations to assess how different parts of the city might respond to seismic events. The findings indicate that seismic waves could be amplified by two to 3.5 times in certain areas, increasing the potential damage during a major Himalayan earthquake. This study is particularly significant as Chandigarh is situated near the seismically active Himalayan belt, a region prone to earthquakes. The underlying geology of the city, characterized by thick sedimentary deposits, further contributes to its vulnerability. The researchers have emphasized that both older, low-rise buildings, often constructed without adequate earthquake-resistant features, and the growing number of multi-storey structures (10-15 stories) need careful evaluation and scrutiny by urban planners and engineers. The study's findings suggest that the bedrock lies at depths of 160 to 200 meters, classifying Chandigarh under Soil Class C, which signifies softer ground conditions prone to enhanced shaking. While Chandigarh has historically been spared major earthquake devastation, the potential impact of future seismic events cannot be underestimated. The study's authors have urged the authorities, including the Union Government and the Chandigarh Administration, to integrate these scientific insights into urban planning and building regulations. This integration is crucial for ensuring that future development adheres to earthquake-resistant design principles and for minimizing potential losses. The research, which involved extensive field investigations using the Horizontal-to-Vertical Spectral Ratio (HVSR) technique at 200 locations across Chandigarh between 2021 and 2023, provides a detailed seismic micro-zonation assessment for the city. The National Centre for Seismology (NCS), India's nodal agency for earthquake monitoring, also conducts seismic microzonation of major urban areas in India that lie in seismic hazard zones, with a priority for 30 cities including Delhi. Chandigarh itself falls under Seismic Zone IV, classifying it as highly susceptible to earthquakes according to the IS 1893 Part-1 (2016) standard and the Bureau of Indian Standards. This classification means the city is considered highly vulnerable to seismic activity, second only to Zone V. Past research and assessments, such as those by the Central Building Research Institute (CBRI) in the mid-2000s, have indicated that some iconic structures like the Secretariat could withstand significant earthquakes, but a comprehensive survey of residential buildings has not been undertaken due to cost concerns. However, older assessments also highlighted that many buildings constructed before the 1990s, when specific guidelines for earthquake-resistant construction were lacking, may be at risk. Experts also note that while the city's generally low-rise nature and quality of older construction might offer some resilience, the increasing trend of multi-storey buildings necessitates a deeper understanding of site-specific seismic behavior. The study's conclusions stress that anticipating patterns of damage and strengthening preparedness measures are essential, especially as Chandigarh continues its expansion. The scientific inputs must be an integral part of development planning to ensure public safety is not compromised. The findings from this study have been submitted to the Union Government and the Chandigarh Administration for further action, aiming to assist policymakers, architects, engineers, and disaster management agencies in creating safer infrastructure and implementing informed land-use strategies. The Indian Institute of Technology (IIT) Roorkee is also actively involved in earthquake engineering research, developing early warning systems and earthquake-resistant building models, underscoring the ongoing efforts in India to mitigate earthquake risks. The National Disaster Management Authority (NDMA) has also conducted mock drills and developed multi-state earthquake disaster scenarios to enhance preparedness in seismically vulnerable regions like Chandigarh and its surrounding states. The findings of this new study serve as a critical reminder of the ongoing seismic risks in Chandigarh and the necessity for robust, science-informed urban planning and building practices to ensure the safety of its residents. The study's submission to governmental bodies signifies a potential for updated policies and stronger disaster management protocols for the region..

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