Tsunami model underestimates shock waves from Tonga eruption


London — This month’s volcanic eruption in Tonga unleashed an atmospheric shock wave radiating at near-sonic speeds, pushing large waves to the coasts of Japan and Peru, thousands of kilometers across the Pacific Ocean.

Predictive models and warning systems designed primarily for assessing waves caused by earthquakes did not take into account the boosting effects of shock waves. According to scientists, this was a serious flaw in these systems, and it was not possible to accurately predict when the waves would land.

Hermann Fritz, a civil engineer at Georgia Institute of Technology, who studies tsunamis, said:

The eruption of Hunga Tonga-Hunga Haapai volcano caused a tsunami, destroyed villages and resorts, and blocked communications for about 105,000 South Pacific countries. Three people have been reported dead.

However, the Tongans were well equipped to cope with the tsunami. The small island nation has been trained for years of tsunamis and is considered the most prepared for natural disasters, knowing that many will evacuate to higher ground.

But in far-flung Peru, for example, the lack of accurate information could have contributed to the deaths of two people drowned in unusually high waves and the catastrophic oil spill from a ship near the La Pampira refinery. There is sex.

“We need to reassess the dangers of tsunamis in other volcanoes around the world,” Fritz said.

For example, a submarine volcano known as Kick’em Jenny is believed to pose a regional tsunami risk to the neighboring island of Grenada in the Caribbean. But in reality, “when a Tongan-type event occurs, it can excite the entire Caribbean Sea and the Gulf of Mexico, and perhaps even the Atlantic Ocean and even the oceans of the world,” he said.

Epoch Times Photo
The overview shows the damage to the building after the volcanic eruption and tsunami in Tongatapu, Tonga on January 16, 2022. (MalauMedia / Reuters)

Tsunamis caused by volcanoes are rare in modern history, and shock waves from Tonga’s volcano are one of the largest ever recorded, as was the one produced by the 1883 eruption of Krakatoa. was.

Prior to the 2018 tsunami following the eruption of Anak Krakatau, volcanic-induced tsunamis had not occurred in the sea for more than a century. Rather, 90 percent of tsunamis are caused by earthquakes.

Therefore, tsunami warning systems are programmed to prioritize seismic events, and scientists measure risk by whether the magnitude of the earthquake is large enough to cause a devastating tsunami (magnitude 7.5 or higher). To do.

Submarine instruments also monitor irregular changes in wave height, transmit information by surface buoys, and then send satellites to the warning center for evaluation.

The Pacific Tsunami Warning Center in Hawaii initially warned of dangerous waves within 1,000 km (621 miles) of the eruption of Tonga. However, their breaking news states, “Because of the source of the volcano, it is not possible to predict the amplitude of the tsunami or the extent to which the danger of the tsunami will spread.” Approximately 10 hours later, the warning was updated to include the possibility of a threat to Peru. Considering that the tsunami near Tonga was relatively small, it was a surprising development.

Gravity-driven tsunamis travel at about 200 meters (660 feet) per second. This is about the same speed as a jet airliner. However, the shock waves from the volcano in Tonga traveled more than 300 meters (186 miles) per second and were so powerful that the atmosphere rang like a bell.

By transferring this energy from the atmosphere to the ocean, shock waves amplified ocean waves around the world, pushing them further away and reducing travel time. Some tsunami warning centers could not respond.

Currently, Fritz said the potential for atmospheric pressure waves needs to be “added to the suite of tsunami warning center modeling and forecasting tools.”

Gloria Dicky

Reuters

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