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[NEW DELHI] A new formula that uses high frequency radar data to detect incoming tsunamis could provide tsunami warnings up to an hour before their arrival at a coastline.

In September last year, researchers studying the tsunami generated by the earthquake in Japan in March 2011, raised hopes of the potential for radar data to detect tsunamis.

Now, researchers at CODAR Ocean Sensors, United States, have developed an algorithm that would automatically detect a tsunami within eight minutes of the wave's arrival in the radar sensor's coverage area.  

The algorithm was tested using data — also generated during the March 2011 earthquake — from 14 high frequency radar sites in Japan and the United States. The findings have now been reported in the journal, Remote Sensing.

Use of the algorithm would enable significant advance warning of tsunamis in locations where shallow waters (less than 200 metres deep) extend well off-shore — for example, across much of South East Asia, the west coast of India and the US east coast — according to Belinda Lipa, the study's lead author.

"Typically, 15 to 30 minutes' advance [warning] can be provided in regions with little continental shelf, where the water gets deep rapidly," Lipa told SciDev.Net. "In regions with a shallow shelf, which extends further offshore, over an hour is possible."

In the open ocean, a tsunami has a low height, an extremely long wavelength and travels at high speeds, and hence can be detected in real time only by pressure sensors at the bottom of the ocean, Lipa explained.

But as it moves towards shallower waters, the wave slows down, and its height and orbital velocity increase, making it detectable by radar.

"High frequency (HF) radar installations at such locations could provide vital capability for the detection and measurement of the local intensity of deadly approaching tsunamis," Lipa said.

She added that HF radar systems are already in place at many coastal locations around the world to monitor surface currents and waves.

"Tsunami-watch software could run in the background, activating a warning should a tsunami be detected, before local infrastructure is damaged," she said.

Basant Kumar Jena, a researcher at India's National Institute of Ocean Technology in Chennai, told SciDev.Net that prior to the 2011 Japan quake, scientists didn't have the data needed to validate the potential inclusion of radar technology in tsunami warning systems.

"The data collected from the various radars along the US and Japanese coasts confirms the capability of HF radars technique to detect tsunamis," he said, adding that the discovery would also enable scientists "to improve the software which detects the tsunami signature from radar data".

Satheesh Shenoi, director of the Hyderabad-based Indian National Ocean Information System, which houses India's tsunami warning system, told SciDev.Net that radar technology would be a valuable addition to multi-faceted tsunami warning systems.

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