Ships at sea could warn of tsunami: UH/PTWC researchers

Undersea sensors are a key tool to measuring tsunami traveling toward Hawai`i, but University of Hawai`i researchers found they are able to detect tsunami from on board ships.

Could that lead to critical new warning data from the hundreds of commercial ships regularly plying the Pacific? That’s possible, according to a study published this month.

(Image: The University of Hawaii research vessel Kilo Moana, which was at sea during the February 2010 Chile earthquake, and which was able to detect the tsunami as it passed under the ship. The Kilo Moana was underway between Hawai`i and Guam. Credit: SOEST/UHM.)

The study, published in the American Geophysical Union’s Geophysical Research Letters, was written by researchers from the University of Hawai`i’s School of Ocean and Earth Science and Technology (SOEST) and the National Oceanic and Atmospheric Administration’s Pacific Tsunami Warning Center. The lead author is James Foster, an assistant researcher at SOEST. Co-authors are Benjamin A. Brooks, Glenn S. Carter and Mark A. Merrifield of SOEST and Dailin Wang of the Pacific Tsunami Warning Center.

Kilo Moana was at sea when the magnitude 8.8 quake occurred. The ship was equipped with highly sensitive geodetic GPS technology. Tsunami waves are generally believed to be undetectable from ships in the deep sea, but can build and be intensely destructive as they move into shallow waters.

When the Chile quake’s tsunami passed under the ship, it was only 4 inches high—smaller than the normal ocean waves. But a tsunami has a characteristic extremely long wavelength. Data collected on the ship was able to pull out of the background movement the change in sea surface height caused by the wave.

“Our discovery indicates that the vast fleet of commercial ships traveling the ocean each day could become a network of accurate tsunami sensors,” Foster said. 

The current best technologies for determining the strength of an underway tsunami  are their appearance on automated tide gauges on islands that lie midway along their paths, and an array of deep ocean pressure sensing DART systems. The DART array is problematic since they are very expensive and difficult to maintain. SOEST in a news release said the DART installation between Hawai`i and Chile at the time of the tsunami was out of order, as was 30 percent of the entire network.

Said Foster:  “If we could equip some fraction of the shipping fleet with high-accuracy GPS and satellite communications, we could construct a dense, low-cost tsunami sensing network that would improve our detection and predictions of tsunamis -- saving lives and money."

 He and fellow researchers at UH SOEST plan to install systems on a couple of ships, to begin collecting data, and to see whether these systems can, in fact, save lives and property, as well as cash. 

The report details: GEOPHYSICAL RESEARCH LETTERS, VOL. 39, L09603, 4 PP., 2012 doi:10.1029/2012GL051367

© Jan TenBruggencate 2012