A sensor network capable of detecting an oceanic earthquake and an impending tsunami in the Indian Ocean is feasible, say experts, but will be useless unless backed by improved communications infrastructure in the countries in greatest peril.
The devastating death toll and damage caused by the tsunami that struck on 26 December 2004 has prompted urgent calls for an early warning system. Indonesia, which has suffered the greatest loss of life in the tragedy – over 80,000 people – has already committed to such a system. And other affected countries and major aid donors are expected to endorse the development of a system at a conference in Jakarta, Indonesia, on Thursday.
The earthquake responsible for the disaster occurred at a tectonic plate boundary a few hundred kilometres west of the Indonesian island of Sumatra. One tectonic plate slid beneath the other, pushing the sea bed about 10 metres upwards. This generated a giant surge that sped to coastlines around the Indian Ocean.
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.
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.
But 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.
“It’s one thing knowing a tsunami is coming and another to warn the population in time,” he told New Scientist. “The real problem is what to do after the red light, which is an infrastructure problem.”
McFadden agrees. “If it’s a tsunami, you’ve got to get the information down to the last Joe on the beach. This is the stuff that is really very hard,” he told the Press Association.
The critical importance of an effective communications system is highlighted by the fact that some people say they were unable to alert the authorities in their countries to the danger of the Asian earthquake. Samith Dhammasaroj, a meteorological expert in Thailand, realised that the massive ocean quake might produce a deadly tsunami but was unable to contact government officials to raise the alarm.
United Nations officials began calling for a tsunami warning system for the Indian Ocean on 29 December. “There is no reason why this cannot be done,” said Sálvano Briceño, director of the UN’s International Strategy for Disaster Reduction. “There is a strong basis of knowledge, technology and collaboration and a real readiness to act.”
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