Tsunami alerts 'confuse public', says Noaa scientist

THE PUNCH Newspaper

Tsunami warnings need to convey information that is more meaningful to the public, a top US researcher says.

Traditional alerts that have focussed on ”wave amplitudes” are confusing to most people, says Dr Vasily Titov.

The scientist, who directs Noaa‘s Center for Tsunami Research, thinks more practical information such as the risk of flooding is also needed.

He says this is one of the key lessons from the recent Magnitude 8.8 Chilean earthquake and subsequent tsunami.

”We‘re scientists and we‘re really proud of our models and our accuracy but we realised after the Chilean tsunami that when we convey this information to the public there is a gap between what we are saying and what is understood,” he told BBC News.

”When we say there is a two-metre wave amplitude expected, the general person imagines a two-metre wall of water.

But that‘s not what amplitude means - tsunami would very rarely come as a wall of water. It refers to the amplitudes at tide gauges and it is peak to trough. It will not be the wave height that a surfer or someone on the beach sees.”

The 27 February quake which had its epicentre some 11 km off the coast of the Maule region of Chile marked a major milestone for tsunami forecasting.

It was the first basin-wide event generated in the Pacific since the Great Alaskan Earthquake of March 1964, and the first occurrence since Sumatra in 2004 when modellers and forecasters could test their capabilities over such a wide area.

At Chile itself, the proximity of the quake to the coastline meant the tsunami arrived within 30 minutes, with water running up some 10 to 15 metres above the expected sea level in places. But even as far away as Hawaii, there was inundation of water with amplitudes of about 2.5m.

The warnings put out by the Noaa Pacific Tsunami Warning Center proved to be highly accurate when the predictions of wave behaviour were checked against what actually happened at tide gauges.

Forecast travel times for the tsunami across the Pacific basin demonstrated an average accuracy of 98%. The forecast of maximum wave amplitudes had an accuracy above 80%.

The modelling and forecasting have become extremely detailed and skilful

This level of success means Noaa could be very confident about its flooding forecasts, which should now be more prominent in the public release of information, said Dr Titov.

”You want to send a message that will be immediately understood and immediately acted upon.


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