Trench, reefs not enough protection: Guam can be hit by tsunamis as high as 19 feet, research says
By Laura Matthews • Pacific Daily News • December 11, 2009
The Mariana Trench and the reefs surrounding Guam aren't enough to protect the island if a tsunami should hit it.
And it could, according to Vasily V. Titov, director of the National Oceanic and Atmospheric Administration's Center for Tsunami Research.
Titov said an 8.5-magnitude earthquake is enough to trigger tsunami waves as high as 19 feet onshore.
"Samoa has answered that question very well; the reef is not a universal protector," Titov said, dispelling years of beliefs that the island's reef system could block the rushing waters from a tsunami.
This determination was made based on the findings from the NOAA's Pacific Marine Environmental Laboratory's research project, which started in 2004, and it was used to create tsunami inundation models for Guam. The researchers used the plate tectonics for Guam and its historical models, among other things, to develop the model. The project was funded by the Pacific Risk Management Ohana.
The full findings will be released before year's end, said Titov, who will leave the island Saturday.
"We can really say where the tsunami is going to be big," Titov said.
So far researchers have developed inundation models for Tumon Bay, Hagåtña, Apra Harbor, Pago Bay and Inarajan.
Should an 8.5 magnitude earthquake shake the island, the Tumon area could get waves as high as 19 feet, while Hagåtña could be washed by waves measuring 15 feet. Meanwhile, waves about 9 feet high could strike Apra Harbor.
The height of the waves will depend on the source of the earthquake. Currently, the researchers are eyeing the Mariana Trench and the Philippine Trench as potential sources.
"That the Mariana Trench can protect you from a tsunami is a misconception. What the trench does is that it straightens the front of the waves and shoots it to the closest coastline," Titov said.
While on the island he will meet with local scientists and technicians to show them how to use the new model, as well as garner more information to support the findings.
Little research exists on tsunami activities on Guam, but some tsunami waves have raced ashore in the past.
According to the data, in 1952 a tsunami generated in the Kamchatka Peninsula in Russia caused little stimulation at Apra Harbor, and again at the same location in 1964 from the Great Alaska earthquake, Titov said.
Chip Guard, the warning coordination meteorologist for the National Weather Service, said the model is a good tool for the island.
"This kind of model will give more specific guidelines that we can work from," Guard said.
Both Titov and Guard said the model must be coupled with public education to make it very effective.