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Predictions Of A Megaquake Rocking The Aleutians

Robert Witter

In the next 50 years, there’s a nine percent chance of an Aleutian-centered earthquake so powerful it could send a devastating tsunami to Hawaii. That’s according to researchers from University of Hawaii at Manoa.

A magnitude 9.0 or greater earthquake is what researchers are referring to. But what does a megaquake look like? Think big. Like Tohoku, the 2011 Japan earthquake and tsunami.

“If there were to be another really, really giant earthquake in the Aleutians it would have the potential to generate like a tsunami like what we’ve seen,” said geologist Rob Witter of the United States Geological Survey.

His work looks at the frequency of past giant earthquakes in the Aleutians -- especially large quakes that may have caused tsunamis. This research can be used for national seismic hazard maps as well as to create tsunami evacuation plans.

While Witter studies what happened in the ancient past, geophysicist Rhett Butler looks to the future. He works on estimating the probabilities of future earthquakes.

When watching video of Tohoku, the University of Hawaii at Manoa geophysicist began wondering if Hawaii had its estimates right. 

“We’re surrounded by the ocean here, so when we’re hit by a very large tsunami wave it affects all sides of the island," Butler said. "If you’re in California you just walk 10 kilometers inland and you hardly notice anything other than it’s a general panic. Here in the Islands all of our roads are along the seashore. We have lots of hospitals. We have airports. It would be an absolute infrastructure disaster.”

An infrastructure disaster that the 2013 State of Hawaii Multi-Hazard Mitigation Plan estimates could cost about $40 billion.

Here in Unalaska, if you feel the ground move, Witter says be prepared to move.

“If you feel strong shaking for 30 seconds of more, you should get to high ground quickly," Witter said. "If you’re in the maritime community or trade, you have to get to deep water fast as well because even in the protected waters of the harbors strong currents can occur and those can cause damage to ports and harbor facilities.”

Butler’s research does not guarantee a megaquake. The pressure in the Aleutian subduction zone could be released by a series of smaller earthquakes.

And he said he’s not trying to scare anyone. He just wants to provide data, so everyone can make informed decisions.

"You like the place you live, it comes with risks," Butler said. "Its good to be aware of the risks. It doesn’t mean its going to happen in your time. The Japanese didn’t think it would happen in their time, so they were surprised."

Zoë Sobel reported for KUCB from 2016 until 2019. She returned to KUCB after a year living in Nepal and Malaysia as a Luce Scholar. She then returned to KUCB as a ProPublica reporter August of 2020 through August of 2021.