Seven years after it built and operationalised an effective tsunami warning system, India is adding another layer of detection mechanism that will ensure near complete certainty in analysing the nature and magnitude of a tsunami in the making.
As it marks the tenth anniversary of the devastating tsunami that hit the eastern coast on December 26, 2004, India is looking back with satisfaction in having created a tsunami warning system that has practically ruled out any large-scale loss of human lives by any similar event in the future.
The Indian Tsunami Early Warning Centre (ITEWC) at the Indian National Centre for Ocean Information Services (INCOIS) in Hyderabad has ensured about two-and-a-half hours of on the mainland to take precautionary measures, including evacuating coastal villages, if necessary.
At the heart of the warning system is its ability to detect a tsunami early. This is done by Bottom Pressure Recorders (BPRs) that India has installed in the ocean about 3,500 metres below the surface near the faultlines where earthquakes are generated. The BPRs record the pressure of water the above them. The ocean surface level changes substantially during a tsunami, thereby changing the water pressure being measured by the BPR. A change in the surface water level of even a centimetre is detected by the BPRs.
While this is the method universally relied upon to detect the generation of tsunamis which has served India’s needs well in the last seven years India is now planning to install GPS-based detection systems in the Andaman and Nicobar Islands to facilitate a second layer of data collection.
Tsunamis are generated only by earthquakes that are a result of vertical movements of tectonic plates. Vertical movements also cause tilts on the earth’s surface along the earthquake’s faultlines. During the 2004 tsunami, for example, some places in the Andaman Islands, which lie along the faultline, got tilted by about a metre. The GPS systems will be able to record such changes on the earth’s surface, and can supplement the observations from the BPRs. This will add additional strength to our system, explained Shailesh Nayak, Secretary, Ministry of Earth Sciences.
Nayak was head of INCOIS when the 2004 tsunami struck, and was the man who built the tsunami warning centre. He said work on installing the GPS-based systems was likely to be complete by October 2015. Around 35 GPS stations, each costing about Rs 20 lakh, will be built in the Andaman and Nicobar Islands.
The GPS systems can give greater accuracy in predicting the magnitude of the tsunami. The 2011 tsunami that hit Japan had been significantly underestimated initially. Though Japan has GPS-based systems, it generally gets very little time to analyse the data. We are lucky that our shores are some distance away from the faultline. The GPS system can be very useful in our case, Nayak told The Indian Express.
The Indian Express ltd.