Increasing importance

The Boxing Day tsunami of 2004, and more recently the 2011 Tōhoku tsunami, have highlighted the extreme vulnerability of coastal populations to these catastrophic natural hazards. With 80% of the world’s population living within 60 miles of the coast and 75% of the fastest growing mega-cities populations located on the coast, the importance of early tsunami detection is only going to increase.

Timely warning

A tsunami wave in deep water (6,000 metres) typically has an extremely long period of 10 mins to 2 hours, and may be travelling at 890kmh-1, but with often with a barely perceptible height of substantially less than one metre. Consequently timely warning depends on early detection of these waves far enough off shore to provide sufficient warning prior to the tsunami reaching shallow water where it rapidly attains its destructive height. Detection of waves in these situations therefore depends on instruments using high resolution pressure sensors on the seabed with integrated low-latency communications to the shore via a surface gateway.

Cost effective operation

The cost of operating a tsunami detection system is largely determined by two factors; duration of deployment between servicing with a ship and satellite communication costs. The former depends on low power systems to maximise deployment duration as well as resistance to biofouling of the surface gateway. The second is mitigated by processing data in situ to identify detections, rather than telemetering all data ashore for processing.

Interoperability

Efforts to provide warnings of tsunamis are coordinated internationally under the auspices of the Intergovernmental Oceanographic Commission. A key programme is US National Oceanic and Atmospheric Administration’s (NOAA) Deep-ocean Assessment and Reporting of Tsunamis (DART) which has historically been used as standard for tsunami messaging systems, and has enabled data from tsunami detection systems to be ingested into the portal maintained by NOAA’s National Data Buoy Center (http://www.ndbc.noaa.gov/dart.shtml)