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Monday, May 20, 2024

High-frequency radar could predict future disaster

The devastation caused by the March 11 earthquake and tsunami in Japan may be avoided in the future with high-frequency radars that track the deadly waves, says a new report. The tsunami swept away cars, ships and buildings as it made its way to the Japanese shore after the 8.9 magnitude earthquake northeast of Tokyo.

“These high frequency radars were first put in place 10 years ago, but the Japan tsunami was the first time this technology could be tested,” said Newell Garfield, director and professor at the San Francisco State University’s department of geosciences.

Scientists from California and Japan detailed the findings of these radars in a recent report published in the August edition of the journal Remote Sensing.

According to the report, models are currently used “for predictions and warning of the arrival of a tsunami.”

However, the predictions of these models are based entirely on the location of the earthquake, leaving little to no time for any safeguard measures.

“The National Oceanic and Atmospheric Administration (NOAA) starts a model which will locate the earthquake and predict if there will be a tsunami, and it will give us a projection of where the tsunami will occur,” Garfield said.

The high frequency radars used by the research team instead look at ocean currents.

“The data signal we obtain from these instruments is then processed by software that can detect the tsunami,” Garfield said.

The instruments also indicate the level of response needed. “You have a trade-off between safety and pragmatism.”

The report claims that the length of the warning time depends on the size of the continental shelf.

The continental shelf is the shallow perimeter of a landmass that lies underwater.

“The waves slow down in this shallow water [and] they increase in height right before they hit the coast,” Garfield said. “Their speed is about the same as the speed of a commercial airliner.”

“California has a very narrow continental shelf,” said John Largier, an oceanographer at the University of California at Davis, Bodega Marine Laboratory. “So we might only have 15 minutes of warning.”

Where the continental shelf is broad, however, there may be as much as a two-hour warning window, giving people enough time to put safety measures in place.

“It could be useful in southeast Asia, the East coast and the western coast of India where the continental shelf is broad,” Largier said.

Largier also pointed out the “bounced wave” impact after the tsunami. The western coast of California was issued a tsunami warning after the Japan tsunami – a potential impact of the “bounced waves” from the disaster.

“These bounced waves are not as easy to predict, but you can see them with these devices and the model can predict their impact,” Largier said. “It can give you local info – how the tsunami is approaching, the amplitude and height of the wave.”

With the software nearly finished in the development stage, the researchers hope to use high frequency radar to avoid future disasters.

“There is a history in the value of this,” Largier said, referring to the research that began almost a decade ago after the Indian Ocean tsunami ravaged Southeast Asia.

SASHA SHARMA can be reached at science@theaggie.org.

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