A small tsunami that reached Australian shores following the devastating earthquake in Chile in February revealed inaccuracies in the predictions of the time and level of tsunami activity, though the warning distribution worked well.
Chris Ryan, co-director of the Joint Australian Tsunami Warning Centre (JATWC), said the mechanics of the centre’s warning system proved effective after the earthquake, with observations and communications systems generating warnings and distributing them effectively in order to notify emergency services and the public.
This included transmission of seismic and earthquake data from Geosciences Australia to the Bureau of Meteorology (the two JATWC partners), after which the Bureau estimated the impact on Australia and issued warnings.
Warnings quickly followed the earthquake, which struck at 5:30pm local time on a Saturday, with the centre sending out its first warning at 7:15pm that evening, and repeated hourly warnings until 5:30pm the next day.
However, it was the magnitude and timing of the tsunami effects on Australian shores that were inaccurate, with the most significant waves arriving three hours later than expected, with their height also lower than predicted.
“Normally we see the largest waves coming reasonably close to our first arrival time - in this case they were three or more hours after our predicted time, so that’s an issue we have to look at,” Ryan said.
The waves were also at “the bottom end of the range” – just over the threshold in some areas of the coast that is required to trigger a low-level warning which predicts a threat to the marine environment.
Ryan said the model, which is an improvement on the predictions that would have been made by a recently replaced system, was being looked at. “We learn something after every event,” he said.
Ryan said he was “disappointed, but not surprised” by Australians who decided to watch the tsunami from the beach.
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