Twenty-nine Indian cities and towns, including Delhi and capitals of nine states, fall under “severe” to “very severe” seismic zones, according to the National Centre for Seismology (NCS). A majority of these places are in the Himalayas, one of the most seismically active regions in the world. Delhi, Patna (Bihar), Srinagar (Jammu and Kashmir), Kohima (Nagaland), Puducherry, Guwahati (Assam), Gangtok (Sikkim), Shimla (Himachal Pradesh), Dehradun (Uttarakhand), Imphal (Manipur) and Chandigarh fall under seismic zones IV and V. These cities have a combined population of over three crore. The Bureau of Indian Standards (BIS) has classified different regions in the country into zones II to V, taking into consideration earthquake records, tectonic activities and damage caused, the director of the NCS, Vineet Gauhlat, said.
The NCS, which records earthquakes and carries out studies pertaining to microzonation of cities, comes under the India Meteorological Department (IMD). Seismic microzonation is the process of subdividing a region into smaller areas having different potential for hazardous earthquake effects. Zone II is considered the least seismically active, while Zone V is the most active. Zone IV and V fall under “severe” to “very severe” categories respectively. Zone V includes the entire northeastern region, parts of Jammu and Kashmir, Himachal Pradesh, Uttarkhand, the Rann of Kutch in Gujarat, parts of north Bihar and the Andaman and Nicobar archipelago. Parts of Jammu and Kashmir, Delhi, Sikkim, northern Uttar Pradesh, West Bengal, Gujarat and a small part of Maharashtra fall under Zone IV.
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Bhuj, which was struck by a massive earthquake in 2001 in which 20,000 people were killed, Chandigarh, Ambala, Amritsar, Ludhiana and Roorkee fall under zones IV and V. Kusala Rajendran, a professor at the Indian Institute of Science (IISc), Bengaluru, and an expert on paleoseismology, earthquake recurrence and active tectonics, said most of the cities in the list have a high population density and fall in the Indo-Gangetic plains. “The Himalayan arc, stretching from the upper Assam region to Jammu and Kashmir, is known to be a high seismic zone and these cities in the Indo-Gangetic belt fall within reasonable limits of the Himalayas. So repercussions are bound to be felt there,” she observed.
M Rajeevan, Secretary, Ministry of Earth Sciences, said 31 new earthquake observatories will come up in the country by March next year. At present, there are 84 observatories. This is being done to detect and record earthquake parameters more accurately and identify possible precursors of tremors. The NCS has also carried out microzonation of cities like Delhi and Kolkata to study the possible impact of earthquake in these mega cities.