BHUBANESWAR: Eastern parts of Bhubaneswar need greater seismic attention because of soft soil and deep underlying bedrock, with high-rise buildings in the area particularly vulnerable to amplified ground shaking, director of the National Centre for Seismology (NCS) Dr G Suresh cautioned on Wednesday.
Highlighting the findings of a recent seismic microzonation study of the capital city, Suresh called for greater attention to earthquake-resistant construction and seismic safety in the eastern parts of Bhubaneswar.
Speaking at the inauguration of a three-day national workshop on Environmental Hazards and Disaster Management at SOA Deemed to be University, he said the NCS study covered 420 sq km of the city’s development plan area. It involved measurements at 1,650 locations, deep borehole investigations and analysis of more than 1,200 soil samples.
The findings revealed that while most parts of Bhubaneswar have stiff ground conditions favourable for building foundations, eastern parts of the city have softer soil, with engineering bedrock located as deep as 86 metres beneath thick alluvial deposits. The area also recorded lower peak frequencies of below 4 hertz, he said.
Explaining the implications, Suresh said tall buildings generally vibrate at lower frequencies. When the natural frequency of a structure matches the frequency of ground motion during an earthquake, resonance can amplify the shaking and increase the possibility of structural damage. He cautioned that although Odisha is often associated with the threat of Bay of Bengal cyclones, its active seismic fault lines also make it vulnerable to earthquakes. A major tremor could cause considerable damage in densely built-up urban areas, particularly where buildings are structurally vulnerable.
Much of Odisha falls in seismic Zone II, while the Mahanadi valley, extending from Jharsuguda and Sambalpur through Angul, Cuttack, Bhubaneswar, Paradip and Puri, comes under Zone III (moderate risk).