Sonardyne International Ltd of Yateley, UK, has delivered the latest batch of acoustic monitoring sensors that will oversee the Indian coastline by providing early detection and warning of tsunami waves.

The network of sensors will be deployed alongside the existing Sonardyne sensors in the Bay of Bengal and off the west coast off India where they will continuously monitor the ocean for the characteristic water pressure changes that indicate a developing tsunami.

The Sonardyne sensors are based upon sophisticated subsea transponders equipped with highly accurate pressure sensors that are positioned on the seabed hundreds of miles off the coast. If one of the transponders detects a small, but continuous change in water pressure, it transmits an emergency warning signal up to a surface radio buoy moored above it. The buoys are operated by NIOT (National Institute of Ocean Technology) of India, and they relay the warnings via a satellite link to the organisation’s headquarters in Chennai. From there, alerts can be forwarded to the appropriate authorities in time for precautions to be taken.

The contract for a tsunami detection system for India was awarded to Sonardyne following an initial trial early in 2007 when systems from Sonardyne and three other manufacturers were evaluated. Only the Sonardyne sensors performed satisfactorily so the company was asked to supply a further eight monitoring transponders which were installed to provide immediate coverage for the areas at most risk. The latest delivery of sensors completes the Indian early warning network and now provides monitoring for the country’s entire coastline.

The success of the Sonardyne system is attributed to its use of proven acoustic technology that is in everyday use in the offshore oil and gas industry. In this area, Sonardyne is a leading supplier of subsea navigation, positioning and communications systems and the company’s Compatt 5 acoustic transponder proved the ideal hardware platform on which to base the tsunami detection sensor.

The reliability of the Sonardyne detection system was convincingly demonstrated to NIOT when the first sensors had only just been laid. The NIOT ship Sagar Manjusha was returning to Chennai after the successful deployment of six tsunami buoys. When the ship was an hour from port, one of the Sonardyne sensors registered a tsunami warning, triggering an alert to NIOT. The vessel was prevented from entering the harbour for berthing and all vessels in Chennai port were evacuated as a precaution. Although in this instance a dangerous tsunami never developed, it was felt that the Sonardyne system had already proven its reliability and effectiveness.

The National Early Warning System for Tsunami and Storm Surges in the Indian Ocean is a collective project initiated by the Ministry of Earth Sciences of India. It was launched following the devastating tsunami of December 2004 and has become a significant demonstration of Indian expertise. Responsibility for development and deployment of the tsunami buoy system and the algorithm for the seabed pressure reference systems was given to NIOT. The tsunami prediction modeling and the final prediction was assigned to the Indian National Centre for Ocean Information Services (INCOIS) in Hyderabad. The use of specialized acoustic technology from Sonardyne has ensured the creation of a system that provides reassurance to vulnerable communities living around the coast of India.