Scientists have found evidence that strong earthquakes in the Aleutian Islands could send an extreme tsunami that could bring huge waves through Waikiki and cripple Oahu's main electrical power plant.
The study from the Hawaii Institute of Geophysics and Planetology at the University of Hawaii and the National Tropical Botanical Garden on Kauai stemmed from the March 2011 earthquake and tsunami that devastated Japan and caused damage in Hawaii.
Cameras caught the devastation as tsunami waves pushed miles inland from the magnitude 9.0 quake off Japan. Now scientists have found evidence that it could happen here.
Archaeobotanist David Burney found it in the Makauwahi Sinkhole on Kauai near Poipu. A cave in the sinkhole had a huge deposit of marine sediment, including shells, gravel and coral, dating back to the 1500s.
Scientists believed the only way they could have gotten there would be by a wave that carried them over the top of the cave, or about 24 feet above sea level.
"There's a spot in the Aleutians that if you have an event there and it is actually capable of doing it, it provides a fairly strong circumstantial case," said Dr. Rhett Butler, interim director of the Institute of Geophysics.
Butler and his team ran computer models, which concluded that such a tsunami could be generated from a 9.2 magnitude quake in a certain spot in the Eastern Aleutians.
"There was a series of very large events that have happened up there about 300, 400 years, and that one in particular had a date that was basically in the same data uncertainty that this Kauai deposit had been dated as," said Butler.
Such a quake would devastate much of Hawaii, but in particular, the study theorizes that it would send a four-story high tsunami through Waikiki.
Butler said it also would wash out the Kahe Power Plant in Leeward Oahu, wiping out power to much of the island.
As for when such an extreme tsunami could happen, no one knows. The Aleutian Islands produce hundreds of earthquakes every year. The last big Aleutian quake affecting Hawaii was in 1946, when a magnitude 8.1 quite triggered a tsunami that killed 159 people.
City management officials said they are looking closely at the study. Officials said there's the possibility that evacuation lines may be expanded to allow for cases of extreme tsunamis.
Butler presented the findings of the study at the annual meeting of the American Geophysical Union in San Francisco.