A new scientific study has raised concerns about the safety of thousands of residential and commercial structures in Chandigarh and its surrounding areas during a major Himalayan earthquake. The research, conducted by scientists from the Central University of Himachal Pradesh, warns that local ground conditions could significantly amplify seismic shaking across the city, increasing the vulnerability of both older low-rise buildings and the rapidly growing number of multi-storey structures.
Study Highlights Seismic Vulnerability
Published in the Journal of Applied Geophysics, the study presents one of the most detailed seismic micro-zonation assessments ever undertaken for Chandigarh. It combines advanced geophysical investigations with geotechnical studies to determine how different parts of the city are likely to behave during strong ground-shaking. The researchers urge authorities to integrate these scientific findings into urban planning and building regulations to minimize future losses.
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.
Building Stock at Risk
According to the researchers, 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. Such information is essential for ensuring that future construction adheres to earthquake-resistant design principles.
Methodology and Findings
Professor A.K. Mahajan, speaking to The Tribune, explained that 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, and five boreholes were drilled for detailed geotechnical analysis.
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 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.
Previous Assessments and Future Steps
Professor Mahajan noted 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.
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.
