Hunga volcano eruption provides an explosion of data – ScienceDaily

The January 15, 2022 massive eruption of the Hunga submarine volcano in the South Pacific Ocean created a variety of atmospheric wave types, including booms heard 6,200 miles away in Alaska. It also created an atmospheric pulse that caused an unusual tsunami-like disturbance that arrived on Pacific shores earlier than the actual tsunami.

These are among the many sightings reported by a team of 76 scientists from 17 countries who studied the atmospheric waves from the eruption, the largest known from a volcano since Krakatau erupted in 1883. The team’s work , compiled in an unusually short period of time due to significant scientific interest in the eruption, was published today in the journal Science.

David Fee, director of the Wilson Alaska Technical Center at the University of Alaska Fairbanks Geophysical Institute, is a lead author of the research paper and among four of the center’s researchers involved in the work.

The eruption of Hunga, near the island of Tonga, provided unprecedented information on the behavior of certain atmospheric waves. A dense array of barometers, infrasound sensors, and seismometers in Alaska – operated by the Geophysical Institute’s Wilson Alaska Technical Center, Alaska Volcano Observatory, and Alaska Earthquake Center – contributed data.

“Our hope is that we will be better able to monitor volcanic eruptions and tsunamis by understanding the atmospheric waves from this eruption,” said Fee, who is also the coordinating scientist for the Geophysical Institute part of the Observatory. Alaskan volcanoes.

“Atmospheric waves have been recorded globally over a wide band of frequencies, and by studying this remarkable dataset, we will better understand the generation, propagation and recording of acoustic and atmospheric waves,” he said. -he declares. “This has implications for monitoring nuclear explosions, volcanoes, earthquakes and various other phenomena.”

The researchers found particularly interesting the behavior of the flare’s Lamb wave, a type named after its 1917 discoverer, English mathematician Horace Lamb.

Larger atmospheric explosions, such as volcanic eruptions and nuclear tests, create Lamb waves. They can last from a few minutes to several hours.

A Lamb wave is a type of guided wave, one that travels parallel along the surface of a material and also extends upward. With the Hunga eruption, the wave traveled along the Earth’s surface and circled the planet four times in one direction and three times in the opposite direction – the same as seen during the eruption. eruption of Krakatau in 1883.

“Lamb waves are rare. We have very few high-quality observations of them,” Fee said. “By understanding the Lamb wave, we can better understand the source and the eruption. It is related to the tsunami and the generation of the volcanic plume and is also likely related to the high frequency infrasound and acoustic waves of the eruption.

The Lamb wave consisted of at least two pulses near Hunga, the first having a seven to 10 minute pressure rise followed by a second larger compression and a subsequent long pressure drop.

The wave also reached Earth’s ionosphere, rising at 700 mph at an altitude of about 280 miles, according to data from ground stations.

A major difference between the Lamb wave from the Hunga explosion and the 1883 wave is the amount of data collected due to more than a century of technological advances and a proliferation of sensors around the world, according to the article.

Scientists noted other findings about atmospheric waves associated with the eruption, including “remarkable” long-range infrasound – sounds too low in frequency for humans to hear. Infrasound arrived after the Lamb wave and was followed by audible sounds in some regions.

The audible sounds, the paper notes, traveled about 6,200 miles to Alaska, where they were heard across the state as repeated booms about nine hours after the eruption.

“I heard the sounds, but at the time I certainly didn’t think it was from a volcanic eruption in the South Pacific,” Fee said.

The Alaskan reports are the furthest documented accounts of audible sound from its source. This is due in part, the paper notes, to the increase in the world’s population and advances in societal connectivity.

“We will study these signals for years to find out how the atmospheric waves were generated and how they propagated so well through the Earth,” Fee said.

Other Geophysical Institute scientists involved in research include graduate student Liam Toney, acoustic wave analysis, figure and animation production; postdoctoral researcher Alex Witsil, acoustic wave analysis and equivalent explosive yield analysis; and seismo-acoustic researcher Kenneth A. Macpherson, sensor response and data quality. All are with the Wilson Alaska Technical Center.

The Alaska Volcano Observatory, National Science Foundation, and US Defense Threat Reduction Agency funded the UAF portion of the research.

Robin S. Matoza of the University of California, Santa Barbara is the lead author of the paper.

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