Hawaii scholars study chances of giant Alaska quake, tsunami

AP News
|
Posted: May 18, 2016 8:10 PM

HONOLULU (AP) — A new study by University of Hawaii researchers says there's a 9 percent chance that an earthquake measuring magnitude 9 or greater will strike Alaska's Aleutian Islands within the next 50 years and send large tsunami waves to Hawaii.

Geophysicist Rhett Butler said Wednesday he thought to do the study after a magnitude 9 earthquake struck off northern Japan in 2011, generating massive waves that killed 18,000 people.

Butler said he began to wonder what the chances were of a similar quake striking the Aleutians and sending a tsunami to Hawaii. The Aleutians are closer to Hawaii than any other subduction zone, or spot where the earth's tectonic plates collide.

Tsunami waves take about four and-a-half hours to reach Hawaii from the Aleutians, which wouldn't give Hawaii residents much time to get ready.

"You potentially have to evacuate a heck of a lot of people. If it happens in the middle of the night, isn't a pleasant thought," Butler said. The Journal of Geophysical Research Solid Earth published Butler's paper this week.

A 2013 report by the state of Hawaii estimated a magnitude-9 earthquake in the Aleutians would cause $40 billion in tsunami damage and affect 375,000 people in the islands.

Butler said it's hard to say how big the waves would be, as their size would depend on the earthquake and the bathymetry of the ocean. But he said evacuation zones for a quake like this would have to be substantially larger than they are currently. The evacuation zones would also have to go much farther inland, he said.

Tsunami waves from a magnitude 9 quake in the Aleutians haven't hit Hawaii in recorded history, but Butler said there's evidence some hit Kauai in the 16th century. He said there appears to be a tsunami deposit near Poipu about 23 feet uphill and about 330 feet from the shore.

Gerard Fryer, senior geophysicist at the Pacific Tsunami Warning Center in Pearl Harbor, said the research was sound. He commended the study for being clear and up front about its assumptions, so anyone who disagrees with the report may input their own assumptions and make their calculations.

Fryer said the study was useful in that it justifies actions government officials have taken to plan for extreme tsunami evacuation zones.

A 1946 earthquake in the Aleutians, measuring magnitude 8.1, generated a tsunami that killed more than 170 people on Hawaii's Big Island, mainly in Laupahoehoe and Hilo where waves averaged 30 feet.