Earthquake hazard map of Delhi released

Earthquake hazard map of Delhi released

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Last week Union Science and Technology Minister Kapil Sibal released a series of new earthquake hazard maps for the capital city of Delhi in India providing area-wise details of the risks that different parts of the city could face in the event of an earthquake. Three regions face the highest risk: the trans-Yamuna area, West Delhi and Chhattarpur area. Four regions face a moderate risk: North-West Delhi, the south Najafgarh region, the areas near Sanjay Nagar in South Delhi, and a long north-south stretch from Timarpur in the north to Sangam Vihar in the south. The trans-Yamuna area faces the highest risk since the water table in the region is shallow, at less than five metres from the ground surface, and consequently in case of an earthquake there is a high chance of the water moving up and mixing with the soil, making the base of buildings weak. As a result, the buildings could sink into the soil. In scientific terms, it is called “liquefaction effect”. The Earthquake Risk Evaluation Centre under the India Meteorological Department, which had prepared the map, is now working towards a more detailed map. When these maps are ready in about two years, one would be able to assess the earthquake risk with greater precision. However just because an area fell in a high-risk zone, it did not mean it was unsafe to live there as buildings could be constructed in such a way that the risk factors were neutralized as techniques are available and any structural engineer would be able to take corrective measures. The new maps would not only be useful for new constructions, existing buildings, which had been built when the entire city was considered as one homogenous region, could also be retro-fitted to make them safe.