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Seismic Intensity map of South India for estimated future earthquakes

It is commonly believed that Southern India is aseismic, i.e. not prone to earthquakes (Seismic - earthquake.) It is true that major earthquakes--the kind that cause widespread damages --are rare in this region. But moderate earthquakes, which can be felt by people, and cause damage to poorly constructed buildings and slight or no damage to well designed structures, can be expected in this area.

In the stable continent region, earthquakes don't usually occur in areas where there has already been a damaging earthquake. As ruptured fault location requires enough time for the energy to build up and cause similar damaging earthquake, which is not frequent in the region having a return period of about 300-500 years and above. This means that past earthquake location needs much time for the energy to build up, before releasing energy to cause a significant earthquake again. So, damaging earthquakes are usually observed in places where seismic activity hasn't been seen before. Scientists constantly strive to advance the science of earthquake prediction so that they can better predict exactly when and where an earthquake might occur.

As a step further in the development of this science, a team of researchers from IISc, led by Dr P Anbazhagan, Asst Professor, Dept of Civil Engg, IISc, have developed the Rupture Based Seismic Hazard Analysis. It is a new kind of analysis to predict earthquakes hazard values. This method considers locations that have experienced minor earthquakes, which may indicate seismic activity, and it also takes into account potential seismic sources. Besides, it eliminates locations that have already seen damaging earthquakes.

With this method, the researchers have arrived at eight probable locations in South India for future earthquakes for a period of next 50 years. They have called these as Future Earthquake Zones based on micro seismicity analysis. In another paper, another team of researchers led by Prof Anbazhagan, have estimated the maximum magnitude of future earthquakes in these eight zones, by taking into account regional rupture characteristics. Using the data from these two papers, Prof Anbazhagan, and others have published a new research paper that was published in the March 2015 issue of the Arabian Journal of Geosciences. In this paper, they have produced a map of the overall seismic intensity of Southern India taking into account the maximum magnitude at each of the eight probable locations of future earthquakes in the area.

Prof Anbazhagan says, "Such information about a probable earthquake zone is necessary in order to seismic design or requalification of important structures and buildings in the area and also for an disaster management planning. If there is an earthquake, there are certain structures that need to stay strong, like hospitals, communication towers, public utility centres, etc. because these need to remain operational all the time. So, this seismic intensity data will be useful in order to build these structures such that they are earthquake-proof. This data will also help in damage estimation and disaster management planning."

Prof Anbazhagan also stresses, "These zones have been identified only based on the available data of the past 150 years. For accuracy, we need data that goes back longer, say 500 to 1000 years."

Contact:

Dr P Anbazhagan. Email: anbazhagan@civil.iisc.ernet.in. Office: 080-22932467; Cell: 09448100410.http://civil.iisc.ernet.in/~anbazhagan/

The papers related to above research have appeared in the journals of Engineering Geology, Journal of Seismology and Arabian Journal of Geosciences.