Tsunami: Signs of 2004 in Nagapattinam. ( Source: Express photo by Oinam Anand) Tsunami: Signs of 2004 in Nagapattinam. ( Source: Express photo by Oinam Anand)

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.

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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.

He said the tsunami warning centre at INCOIS, designed and developed indigenously, had worked perfectly in the last seven years, sending out information to authorities in India and 22 other countries in South and South-east Asia and the Middle East about earthquakes being generated in the Indian Ocean region, and whether they were likely to produce tsunamis.

“We cannot prevent tsunamis from being generated or hitting the coastlines, but by providing accurate information in real time to countries which are likely to be affected, we can minimize the damage to a very large extent. Destruction of immovable property along the shores might still be inevitable in some cases, but I think we have put systems in place that will ensure that large-scale loss of human lives, like the way it happened in 2004, are completely avoided. In that sense, I think, the tsunami warning system, along with the work of several disaster management agencies, has made India tsunami-proof,” Nayak said.

In 2004, an earthquake measuring 9 on the Richter scale in the Bay of Bengal triggered one of the biggest tsunamis ever, with waves several metres in height. It killed more than 200,000 people in about 15 countries in the region, including more than 10,000 in India.

Nayak said the absence of an early warning system in India at that time was not because of any lack of capability or expertise, but because no one had thought that a tsunami of that size could ever hit India. Not much is known about the last major tsunami to hit India, in the 1880s. The tsunami that hit the western coast in 1945 too is poorly documented.

Immediately after the 2004 tsunami, the government authorized the setting up of a tsunami warning centre. INCOIS, which provides a variety of other ocean-related information, was a natural choice for the centre which was built within three years at an initial capital cost of less than Rs 100 crore.

Even before its formal inauguration in October 2007, however, the early warning system faced its first test — and passed. On September 12, it issued an alert saying a small tsunami with waves about 20 cm high was headed towards Chennai. Waves of 18 cm height did indeed hit Chennai.

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