How does a Tsunami Early Warning System work ?

By Richard Ingham in Paris
Wednesday, 05 January , 2005, 10:29

A tsunami alert system is a combination of real-time sensors, data-crunching computers, orbiting satellites -- and the nuts-and-bolts task of training the public to respond to warnings.

This mix of silicon and psychology is already in place in the Pacific Ocean and will be the format for providing the Indian Ocean with its own early-warning system, experts say.

The first political steps towards setting up a regional warning network are likely to be taken at a major summit in Jakarta on Thursday to discuss the relief effort for the December 26 disaster.

That will be followed up with technical work among large countries at the final day of a UN-sponsored World Conference on Disaster Reduction, taking place in Kobe, Japan, from January 18-22, the organisers told AFP Tuesday.

"A tsunami early warning system is not a top-down, instrument-only initiative," Reid Basher of the UN's International Strategy for Disaster Reduction (ISDR) told AFP in an interview from Bonn.

"The biggest challenge is how to get the message across to people at risk and to get them to respond." The matrix for the Indian Ocean network is the Tsunami Warning System (TWS), operating in the Pacific since 1968.

When an earthquake occurs, participating states send seismic data to a centre based in Hawaii, which assesses whether the temblor's location and severity could generate a tsunami.

If so, it sends out a warning of an imminent hazard, detailing the wave's predicted arrival at estimated coastal locations within a given time. This information is supplemented by tidal gauges, buoys and pressure sensors that are scattered around coastlines and on the ocean floor.

These detect the passage of a big wave and radio the data back to the national and regional centre, thus fine-tuning knowledge as to the size of the wave, its direction and speed. If no wave is detected, the warning is cancelled.

In many countries, setting up the system of seismographs and wave monitors will be the biggest expense, said Basher.

"In many places, the existing instruments are used for scientific research or as historical gauges of sea levels. They have to be upgraded, so that they provide real fast, real-time monitoring."

But hi tech is only one phase of a tsunami alert system. A country may well receive an early warning, several hours or more before a Great Wave strikes.

But to make use of it, that country has to have an efficient national alert system, with equipment which functions, with competent officials and a public trained to respond swiftly and without panic, Basher said.

It means carrying out awareness campaigns in homes, schools, hospitals and businesses in vulnerable regions.

This is the time-honoured business of using posters, radio and TV messages and carrying out occasional training exercises, advising people to evacuate to higher ground, not to head to the beach to watch the incoming wave and to stay tuned to local media until the emergency is over.

For a monitoring system to operate in the Indian Ocean, "at least four or five countries" would be needed to pool their efforts. Fewer than that means there would be insufficient coverage of the region, said Basher. He put costs at "at least a few million" dollars per country per year.

Such investment is worth it, says Frank Gonzalez, a tsunami researcher at the US National Oceanic and Atmospheric Administration's Pacific Marine Environmental Laboratory in Seattle. "The commitment needed is not insignificant for a country or an international community, but there is no doubt in my mind that tens of thousands of lives would have been saved in Asia," he said last week.

The Indian Ocean is not the only place to be lacking a tsunami alert. The system is also absent in the Mediterranean and Atlantic, both of which are vulnerable to rare but potentially murderous giant waves, according to scientists.