Seismic Mapping of India

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• A total of ~59% of the land mass of India (covering all states of India) is prone to earthquakes of different intensities. As per the seismic zoning map of the country, the total area is classified into four seismic zones.

• Zone V is seismically the most active region, while zone II is the least. Approximately, ~ 11% area of the country falls in zone V, ~18% in zone IV, ~ 30% in zone III and remaining in zone II.
• The National Centre for Seismology under the Ministry of Earth Sciences is the nodal agency of the Government of India (GoI), for monitoring earthquakes in and around the country.
• For this purpose, NCS maintains a National Seismological Network (NSN) consisting of 115 observatories spread across the country.
• The information of earthquakes reported by NCS is being disseminated to the concerned central and state disaster authorities in least possible time to initiate the adequate mitigation measures.
• Secondly, Seismic Microzonation of cities in India having population of 5 Lakh and above is also considered. The purpose is to generate inputs for constructing earthquake risk resilient buildings/structures to reduce and mitigate the impacts of earthquake shaking and for minimising the damages to structures and loss of lives for safer urban planning.
• Additionally, the National Disaster Management Authority (NDMA) of India is engaged in conducting regular awareness campaigns every year through print, electronic as well as social media from time to time to sensitize programs on prevention and preparedness for building safety from earthquakes.
• Besides, the Government of India is poised to follow guidelines by the Bureau of Indian Standards (BIS), Building Materials & Technology Promotion Council (BMTPC) and Housing and Urban Development Corporation (HUDCO) etc. for the design and construction of earthquake risk-resistant structures to minimize the loss of life and damage to property caused by earthquakes.
• These guidelines are in wide circulation among the public and the administrative authorities responsible for the design and construction of earthquake-resistant structures in earthquake-prone areas.
• The seismic Zonation map of the country (state-wise) given by the Bureau of Indian Standards (BIS) has been categorised into several seismic zones (Zone II to Zone V) with the variability of peak ground acceleration (PGA) (0.16g to > 0.36g) with of 10% of exceedance in PGA in 50-years as shown in the figure below. According to this map, the state of West Bengal falls under Zone IV, III and II. A larger portion of West Bengal state lies in Zone III. The state of Uttar-Pradesh, the state lies in Zone IV, III and II.
• The seismic zones of the entire country including West Bengal are classified based upon the empirical seismic attenuation law with respect to the maximum credible earthquake source zone located in the vicinity of the area under study, which has further corroborated with historical seismicity and ground motions of the earthquakes observed in various parts of the country in past. This data was analysed by the Bureau of Indian Standards to prepare a Probabilistic Seismic Hazard Zonation Map of India.