Scientists say the Tongan underwater volcano eruption shows the need for forecasting models and warning systems to factor in atmospheric pressure waves.
The volcanic eruption in Tonga this month unleashed an atmospheric shockwave that radiated out at close to the speed of sound, pushing large waves across the Pacific to the shores of Japan and Peru, thousands of kilometres away.
Forecasting models and warning systems, designed primarily to assess earthquake-triggered waves, did not account for the boosting effects of the shockwave.
It was a critical flaw in these systems, scientists said, leaving them unable to predict exactly when the waves would hit land.
‘The trans-Pacific and global waves arrived earlier than forecast, which (was) terrible for distant shorelines,’ said civil engineer Hermann Fritz at Georgia Tech University, who studies tsunamis.
The Hunga Tonga-Hunga Ha’apai volcano eruption triggered a tsunami that destroyed villages and resorts and knocked out communications for the South Pacific country of about 105,000 people.
Three people have been reported killed.
However, Tongans were well equipped to deal with the tsunami.
The country is considered among the most prepared for natural disasters, with years of tsunami drills under its belt, and many people knew to move to higher ground.
But for faraway Peru, for example, the lack of accurate information may have contributed to the death of two people who drowned in unusually high waves as well as the catastrophic oil spill from a ship near La Pampilla refinery.
Tsunami waves, driven by gravity, travel at about 200 metres per second – roughly the speed of a jetliner. But the shockwave from Tonga’s volcano had moved at more than 300 metres per second and was so powerful, scientists said, that it caused the atmosphere to ring like a bell.
Through the transfer of this energy from the atmosphere to the ocean, the shockwave amplified ocean waves around the world, pushing them farther afield and accelerating their travel time – something tsunami warning centres weren’t equipped to handle.
Now, Fritz said, the possibility of atmospheric pressure waves needs to ‘be added to tsunami warning centres’ suite of modelling and forecasting tools’.