New deep sea Tsunami-detecting system speeds detection, response

Researchers have developed a sea floor pressure recording system that measures ocean depths and promises to detect tsunamis faster while providing ever-earlier warnings to coastal communities.

Gizmo of the tsunami detection ilk

The system, known as the pressure-based acoustically coupled tsunami detector (PACT) for real-time detection of sea level rises in the deep ocean, was successfully tested near the Canary Islands earlier this month, signaling a milestone in the development of the Indian Ocean Tsunami Early Warning System, researchers said in a news release.

Scientists of the Alfred Wegener Institute, in collaboration with companies Optimare and Develogic, and with the Zentrum für Marine Umweltwissenschaften (MARUM) and the University of Rhode Island, are developing parts of the project.PACT consists of a reliable, compact and highly energy efficient system that records and analyzes seafloor pressure every 15 seconds. It then transmits the information to the surface modem if a tsunami event is detected. Similar to a fax machine, an acoustic modem uses a sequence of sounds - the so-called telegram - to transmit information to a second modem which is connected to a buoy near the surface, sending the data via satellite to the warning center, the group said in a release.

PACT is unique in that it processes a multitude of information as the basis for a comprehensive and accurate evaluation of every particular situation. Within just few minutes, measurements of the vibrations and horizontal seafloor movements off the coast of Indonesia provide a clear picture of the location and intensity of a seaquake, which, at the warning centre, facilitate the appropriate selection of a previously calculated tsunami propagation model. However, not every seafloor quake causes a tsunami. There is only one way to be clear about this and avoid nerve-wrecking and costly false alarms: we must measure sea level directly, researchers said.

During the Canary Island test, the system worked at depths over 10,000 feet deep. Over periods of several days, pressure data were transmitted repeatedly to the surface modem and none of the data telegrams were lost, a crucial requirement for the reliable functioning of the warning system, the group said. The PACT system will undergo further testing at this point mostly aimed at seeing how it responds during the winter storm season.

Many scientific agencies world-wide are contributing to tsunami early warning systems. The National Oceanic and Atmospheric Administration for example last year launched the Deep-ocean Assessment and Reporting of Tsunami buoy station in the Indian Ocean to assist in detecting tsunamis.

The DART system provides real-time tsunami detection as waves travel across open waters. According to a NOAA press release, the stations consist of a bottom pressure sensor that is anchored to the seafloor and a companion moored surface buoy. An acoustic link transmits data from the bottom pressure sensor to the surface buoy, and then satellite links relay the data to ground stations.

According to NOAA, since 1850 alone tsunamis have been responsible for the loss of more than 420,000 lives and billions of dollars of damage to coastal structures and habitats. Most of these casualties were caused by local tsunamis that occur about once per year somewhere in the world. For example, the Dec. 26, 2004, tsunami near Thailand killed about 130,000 people close to the earthquake and about 58,000 people on distant shores. Predicting when and where the next tsunami will strike is impossible but the idea is these sensor networks will help avert calamity and give localities early warning to evacuate as many people as possible.

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Copyright © 2007 IDG Communications, Inc.

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