Thousands of residential and commercial structures in Chandigarh and its surrounding areas could face heightened risk during a major Himalayan earthquake, with a new scientific study warning that local ground conditions may significantly amplify seismic shaking across the city.The study, conducted by researchers from the Central University of Himachal Pradesh, has highlighted that both older low-rise buildings lacking earthquake-resistant features and the rapidly increasing number of multi-storey structures in Chandigarh and its vicinity require closer scrutiny from planners and engineers. The researchers have urged the authorities to integrate scientific findings into urban planning and building regulations to minimise future losses. Published in the Journal of Applied Geophysics, the study presents one of the most detailed seismic micro-zonation assessments undertaken for Chandigarh. It combined advanced geophysical investigations with geotechnical studies to determine how different parts of the city are likely to behave during strong ground-shaking.According to the researchers, Chandigarh’s location near the seismically active Himalayan belt, coupled with its underlying geology, makes it particularly vulnerable to earthquake hazards. While the city has largely escaped major destruction in the past, the potential impact of future Himalayan earthquakes cannot be overlooked.The study states that many older two-storey buildings constructed using burnt brick masonry without adequate anti-seismic measures remain susceptible to damage. At the same time, the city’s expanding skyline, marked by framed structures and high-rise buildings of 10 to 15 storeys, underscores the importance of understanding site-specific seismic behaviour. The researchers said such information is essential for ensuring that future construction adheres to earthquake-resistant design principles. Professor AK Mahajan, while talking to The Tribune, said the team carried out extensive field investigations between 2021 and 2023. Ambient noise measurements using the Horizontal-to-Vertical Spectral Ratio (HVSR) technique were conducted at 200 locations across Chandigarh. In addition, Multiple Simulations with One Receiver (MSoR) surveys were carried out at 40 sites, Multichannel Analysis of Surface Waves (MASW) studies at 16 sites, while five boreholes were drilled for detailed geotechnical analysis, he said.The findings revealed that Chandigarh is largely underlain by soft alluvial deposits comprising clay, sand, gravel and silt resting above deeper Siwalik bedrock. Such geological conditions can intensify earthquake shaking professor AK Mahajan said.Researchers found that the city’s fundamental frequency ranges from 0.84 to 1.09 Hz, while the site amplification factor varies between 2 and 3.5. This indicates that seismic waves reaching the surface could become two to 3.5 times stronger in certain areas because of local soil conditions. The study also estimated that the underlying bedrock lies at depths ranging from 160 to 200 metres, suggesting the presence of thick sedimentary deposits beneath the city. Based on measured shear-wave velocities, Chandigarh was broadly classified under Soil Class C, representing relatively soft ground conditions that may experience enhanced shaking during earthquakes. Professor Mahajan said that previous seismic hazard assessments for Chandigarh were mostly based on regional studies and limited field data. The latest investigation fills that gap by generating high-resolution maps depicting local variations in soil properties, amplification levels and expected seismic response. The studies have been submitted to the Union Government and Chandigarh Administration for further action, he said.The researchers said the findings could assist policymakers, architects, engineers and disaster management agencies in developing safer infrastructure and informed land-use strategies.The study concluded that understanding how different parts of Chandigarh are likely to respond during future Himalayan earthquakes can help authorities anticipate patterns of damage and strengthen preparedness measures well in advance.As Chandigarh continues to expand, the researchers stressed that scientific inputs must become an integral part of development planning, ensuring that growth does not come at the cost of public safety.