India pushes for micro-level earthquake vulnerability maps

Launches seismic microzonation manual

 
By Dinsa Sachan
Last Updated: Saturday 04 July 2015

Shaken by the recent 6.9 magnitude earthquake that rocked Sikkim, the Centre has issued a seismic microzonation manual that outlines guidelines for mapping vulnerability of areas in the country to the natural disaster. It provides microzonation and urban planning protocol for geoscientists, engineers and builders across the country.


Centre has issued a seismic microzonation manual that outlines guidelines for mapping vulnerability of areas in the country to the natural disaster.
Microzonation takes into account seismic hazard assessment at the city level
It helps identify which areas in a particular city are more prone to destruction in the event of an earthquake. This information can be applied to building purposes
 
The seismic zoning map of India prepared and updated by the Bureau of Indian Standards divides the country into different seismic zones depending on their vulnerability to earthquakes. “The macro-level seismic classification of the country is too broad and not very helpful for practical purposes. That’s where microzonation comes in,” says Harsh Gupta, former secretary with the earth sciences ministry.
Microzonation takes into account seismic hazard assessment at the city level. “It helps us identify which areas in a particular city are more prone to destruction in the event of an earthquake. This information can be applied to building purposes,” he adds. India is classified into four zones—II to V, in increasing order of seismic vulnerability. Microzonation is of paramount importance for zones that have high seismic activity beneath.

Gupta notes that areas in a city which have a thick pile of sediment above the bed rock are more prone to destruction in the event of an earthquake. “If we find that important government buildings are in vulnerable zones, they could be made safer using retrofitting,” he says. Retrofitting involves adding structures like shear walls in buildings to make them earthquake resistant.

“We have done our job by issuing microzonation suggestions and now the onus is on the urban development ministry to incorporate information generated by microzonation studies into urban planning,” said Vilasrao Deshmukh, Union earth sciences minister at the launch of the manual. He also called for setting up of a separate government authority to give clearance for construction of property in earthquake prone areas. “Construction in cities like Delhi and Mumbai should not be permitted unless this authority gives approval,” he added.

Seismic microzonation was initiated in the country two decades back. Microzonation of Sikkim was undertaken in 1996 by the department of science and technology. The ministry of earth sciences has been handling microzonation responsibilities after its formation in 2006. In 2008, the ministry formed a National Steering Committee to provide guidance for microzonation studies across select cities. Under this initiative, microzonation work has been conducted in several cities including Bengaluru, Dehradun and Ahmedabad. The microzonation exercise has been going on in Delhi for the past decade. Detailed microzonation of the city is being carried out by the Earthquake Risk Evaluation Centre (EREC) under the supervision of the India Meteorological Department and is scheduled to be completed in the next two years.
Several institutes have been carrying out microzonation studies independently and the manual will provide a uniform set of guidelines for such initiatives. "It can also be consulted by urban development authorities for construction purposes," says S K Nath co-author of the manual.

 

Subscribe to Weekly Newsletter :

Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.