On the south side of the Hawaiian island of Kauai lies Makauwahi, a massive cave and sinkhole where scientists have uncovered evidence of an enormous tsunami that struck Hawaii about 500 years ago.

Triggered by a 9.0-magnitude earthquake off the coast of the Aleutian Islands in Alaska, the tsunami likely brought waves up to 30 feet — enough to devastate Hawaii’s coastal populations, infrastructure and economy today.

A new study says there’s a chance it will happen again within 50 years.

A tsunami warning sign in Kona.
A tsunami warning sign in Kona. Chad Blair/Civil Beat

The study, published in the Journal of Geophysical Research, involved a team of researchers at The University of Hawaii at Manoa who analyzed fault length and plate-convergence rates to estimate the likelihood of a mega-earthquake (magnitude 9 or greater) in the Aleutian Islands.

The findings suggest there is a 6 to 12 percent chance of a mega-earthquake striking the Aleutians and causing a tsunami in Hawaii in the next 50 years. If and when it happens, it could cause some $40 billion in damage and affect 400,000 residents and tourists.

Lead author Rhett Butler, a geophysicist at the UH School of Ocean and Earth Science and Technology, said in a statement that he and his team devised their model precisely because Hawaii has no recorded history of mega-tsunamis.

“Necessity is the mother of invention,” Butler said.

The researchers validated their model by using data from the five largest tsunamis since 1900 — Kamchatka, 1952; Chile, 1960; Alaska, 1964; Sumatra-Andaman, 2004; and Tohoku, 2011— as well as evidence found in geological samples, including some from the Makauwahi sinkhole.

The team said it hopes the findings will help Hawaii officials prioritize the potential of a tsunami threat with other risks. It is also considering ways to estimate the threat of smaller-magnitude earthquakes in the Pacific.

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