New Scientist - Tsunami warning system is not simply sensors
New Scientist - Tsunami warning system is not simply sensors: "An early warning system for tsunamis is already in operation in the Pacific Ocean and consists of a network of seismograph and tidal gauges linked via satellite to monitoring centres based in Alaska, US, and Hawaii.
Seismographs provide the first line of defence, alerting monitoring staff to any earthquakes large enough to produce a tsunami. But not every such quake produces these deadly waves, so tidal gauges that record changes in ocean depth are then used to determine whether a tsunami is actually on its way.
However, a problem with the system is that three in four tsunami alerts are false alarms. Evacuations in such cases are costly and can breed complacency."
Pressure sensors
A more accurate monitoring system, developed by the US National Oceanic and Atmospheric Administration, began operational use in 2003 and has been incorporated into the Pacific Ocean early warning system. Deep Ocean Assessment and Reporting (DART) sensors use deep-sea pressure detectors that measure changes in water depth as a tsunami wave passes overhead.
The sensors then transfer the information to a surface buoy, which relays it to the monitoring stations by satellite. The DART system prevented a false alarm on Hawaii just a month after its activation, following a tremor in Alaska. DART is also less vulnerable to earthquake damage than tide gauges but experts insist that multiple detection systems are essential.
Officials from the Pacific Tsunami Warning Center in Hawaii detected the seismic signal from the earthquake on 26 December but were unable to determine when or where a tsunami might strike. Only after hearing media reports that a tsunami had hit Sri Lanka were they able to alert Madagascar and the Mauritius Islands via the State Department in Washington, DC, US.
Phil McFadden chief scientist at Geoscience Australia, which has been commissioned by the Australian government to design an early warning system for the Indian Ocean, says it could consist of 30 seismographs to detect earthquakes, 10 tidal gauges and six DART buoys. He estimates that it would only cost around $20m to install these sensors.
ut installing a detection system is only one part of the challenge, says David Ovadia, head of British Geological Survey International in Nottingham, UK. He says it is also vital to have a reliable communications system and to educate people about what to do after the alarm is raised.
Seismographs provide the first line of defence, alerting monitoring staff to any earthquakes large enough to produce a tsunami. But not every such quake produces these deadly waves, so tidal gauges that record changes in ocean depth are then used to determine whether a tsunami is actually on its way.
However, a problem with the system is that three in four tsunami alerts are false alarms. Evacuations in such cases are costly and can breed complacency."
Pressure sensors
A more accurate monitoring system, developed by the US National Oceanic and Atmospheric Administration, began operational use in 2003 and has been incorporated into the Pacific Ocean early warning system. Deep Ocean Assessment and Reporting (DART) sensors use deep-sea pressure detectors that measure changes in water depth as a tsunami wave passes overhead.
The sensors then transfer the information to a surface buoy, which relays it to the monitoring stations by satellite. The DART system prevented a false alarm on Hawaii just a month after its activation, following a tremor in Alaska. DART is also less vulnerable to earthquake damage than tide gauges but experts insist that multiple detection systems are essential.
Officials from the Pacific Tsunami Warning Center in Hawaii detected the seismic signal from the earthquake on 26 December but were unable to determine when or where a tsunami might strike. Only after hearing media reports that a tsunami had hit Sri Lanka were they able to alert Madagascar and the Mauritius Islands via the State Department in Washington, DC, US.
Phil McFadden chief scientist at Geoscience Australia, which has been commissioned by the Australian government to design an early warning system for the Indian Ocean, says it could consist of 30 seismographs to detect earthquakes, 10 tidal gauges and six DART buoys. He estimates that it would only cost around $20m to install these sensors.
ut installing a detection system is only one part of the challenge, says David Ovadia, head of British Geological Survey International in Nottingham, UK. He says it is also vital to have a reliable communications system and to educate people about what to do after the alarm is raised.
posted by Hugh W at 5:10 PM
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