Earthquakes are one of the worst natural disasters and the Nepal earthquake of last week reminds us how nature can affect us. People take many things for granted while designing homes and buildings in the cities but they should keep in mind that there are few protocols to be followed to make the building stronger and resistant to natural disasters.
Chennai has a moderate level risk of earthquake and the closeness to shoreline makes it more risky. The increase in population in the city also adds to risks because many buildings are being built and not all of them follow the construction norms correctly. Many new flats in Chennai are being built mainly close to the sea and there comes in the risk of a loose sand foundation. When the sand is loose, the foundation must be deeper and stronger so as to withstand any natural disaster. But not many builders today plan their buildings that way in order to save money. There are certain norms for building more than few floors. According to the norms, columns of stilt floors should be a minimum of 300mm or 1ft wide. They should be at least 1m wide for buildings with 10 storeys or more.
When the buildings are old and do not have the requirements, the authorities need to retrofit them. Retrofitting a building involves increasing the width of columns. This may come up to 25% of the building’s cost; however constructing an earthquake resistant building costs only 15% more. Buildings should go through fire safety tests as earthquakes cause fire due to electrical short-circuits.
In Chennai, areas like Adyar, Besant Nagar, OMR and ECR which are close to the sea must definitely have the specified norms in order to have earthquake resistant buildings.
