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New volcanic eruption detection device installed, picks up other natural phenomenon

 Fireweed & Redoubt Volcano-Cindy Rombach
Fireweed & Redoubt Volcano-Cindy Rombach (KTUU)
Published: Dec. 27, 2020 at 8:50 PM AKST
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ANCHORAGE, Alaska (KTUU) - The Alaska Volcano Observatory (AVO) has expanded the eruption detection capability in Cook Inlet.

Earlier this year, the new array was installed on the Kenai Peninsula between Nikiski and Kenai.

Its an array of six low frequency microphones that detect infrasound.

John Lyons, a research geophysicist at the AVO, said infrasound is anything below 20 hertz, which is the cutoff of what humans can hear, but volcanoes make a lot of this type of sound when they erupt. While not audible, it can be heard when it is sped up.

The sensors on one array are each spaced about 150 to 300 feet apart. Together they work similar to how our ears do.

“Just like when someone is talking to our left or to our right, there’s a little bit of a time lag between the arrival at one ear and the other,” Lyons said. “Our brain processes where that sound is coming from when we turn our head. The array does the same thing, but it processes where this infrasound is coming from, and then we use that to figure out if there’s a sound signal coming from an active volcano.”

The array’s basic function is to give real time alarms and information on volcanoes erupting in cook inlet, but it can pick up any type of infrasound.

“In addition to eruptions, it also it picks up things like large landslides, avalanches, large floods potentially,” Lyons said. Right after it was turned on, it picked up a fireball exploding in the atmosphere.

Lyons said you can think of infrasound as like a mass of material — like a landslide — pushing a lot of atmosphere out of the way.

This is the seventh eruption detection array of it’s kind in the areas from Adak to Dillingham, Lyons said.

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