Is Hawaii at risk for experiencing a tsunami? New research finds that a powerful earthquake in Alaska sent large waves up to 30 feet (9 meters) high crashing down on Hawaii about five centuries ago, leaving behind fragments of coral, mollusk shells and coarse beach sand in a sinkhole located on the island of Kauai.
The quake, thought to be a magnitude of 9.0, sent the towering waves towards Hawaii sometime between 1425 and 1665, the study found. It’s possible that another large Alaskan earthquake could trigger a similar tsunami on Hawaii’s shores in the near future, experts stated.
The tsunami was at least three times the size of the damaging 1946 tsunami, which was created by an 8.6-magnitude earthquake off the Aleutian Islands. Mammoth tsunamis, as described in this study, are rare, and likely take place once every thousand years. There’s a 0.1 percent chance it could take place any given year, the same probability that northeastern Japan had for the 9.0-magnitude 2011 Tohoku earthquake and related tsunami, said Gerald Fryer, a geophysicist at the pacific Tsunami Warning Center in Ewa Beach, Hawaii, who did not partake in the study.
Results of the study already have Honolulu officials up in arms, revising their tsunami evacuation maps, Fryer said. The new maps, which will affect nearly 1 million people who reside in Honolulu County, would include more than twice the area of evacuation I some areas, Fryer said in a statement. County officials hope to distribute the new evacuation maps by the close of 2014, Fryer said.
Researchers will likely find more evidence of the large tsunami, Fryer said. “I’ve seen the deposit, ” Fryer said. “I’m absolutely convinced it’s a tsunami, and it had to be a monster tsunami.”
“You’re going to have great earthquakes on planet Earth, and you’re going to have great tsunamis,” said the study’s lead researcher, Rhett Butler, a geophysicist at the University of Hawaii at Manoa. “People have to at least appreciate that the possibility is there.”
Evidence of the colossal tsunami surfaced in the late 1990s during the excavation of the Makauwahi sinkhole – a collapsed limestone cave off the south coast of Kauai. About 6.5 feet (2 meters) below the surface, study researcher David Burney found a plethora of old debris that came from the ocean.
The study was published Oct. 3 in the journal Geophysical Research Letters.