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November 2005

U.S. Expanding Tsunami Alert Network

By Grace Jean

The United States plans to expand its tsunami warning system capabilities by deploying new technology to detect and monitor such waves in the Pacific, Caribbean and Atlantic basins.

The government has pledged $37.5 million over the next two years for the project, which includes the production and deployment of 31 new DART buoys, (Deep-Ocean Assessment and Reporting of Tsunamis) manufactured by Science Applications International Corporation.

There are currently six DART buoys in operation in the Pacific Ocean, with three in the Gulf of Alaska, two off the coast of Oregon and one in the deep waters of Oahu, Hawaii. The National Oceanic and Atmospheric Agency jointly operates another buoy in the southern Pacific with Chile.

“The DART technology is the only technology in the world that we know works,” said Laura Kong, director of the International Tsunami Information Center, based in Honolulu, Hawaii.

According to Kong, two other countries—Germany and India—have developed DART-like technologies. But these technologies have not been scientifically documented. In August, Germany unveiled an instrument that it plans to deploy for the first time off the western coast of Sumatra, Indonesia. India has yet to deploy its technology.

The U.S. DART system measures waves in the open ocean. It links two components: a sensitive pressure sensor, called a tsunameter, that sits at the bottom of the ocean, and a buoy that transmits pressure data to the country’s two warning centers.

“It’s the only direct measurement of a tsunami wave,” said Christian Meinig, director of engineering at NOAA’s Pacific Marine Environmental Laboratory. He helped to develop, design and build the original DART technology at PMEL.

This month, SAIC begins work on the new system, known as DART 2, according to Chuck Fralick, operations manager at the company.

DART 2 has a two-way communications link, said Meinig. The original DART system could only transmit data, he said. With the new system, someone at the warning center can initiate communication with the buoy. For instance, if there was a seismic event, you could tell the buoy to go into a high state of recording, he said.

DART 2 also incorporates new technology to double the life span of the electronic systems. Before, the buoy systems lasted one year, its deep ocean sensors for two. Now the systems can last two years and four years, respectively, said Fralick.

The current DART buoys transmit information via NOAA’s high-power, 40-watt Geostationary Operational Environmental Satellite (GOES). The new system will transmit using an Iridium commercial satellite.

Far below the surface of the ocean, the tsunameters can detect small changes in pressure, such as a wave smaller than 1 centimeter high, passing over.

“They have a resolution of a quarter millimeter,” said Meinig.

Tsunameters sit upon the seafloor, 2,000 to 6,000 meters beneath the ocean’s surface, held in place by a 720-pound anchor. The package includes a bottom pressure recorder, a computer and a transducer. Nearby, a moored 2.5-meter disk buoy carries an acoustic modem to communicate with the tsunameter. The buoy sends information via satellite to the National Data Buoy Center, the Richard H. Hagemeyer Pacific Tsunami Warning Center in Ewa Beach, Hawaii, and the West Coast/Alaska Tsunami Warning Center in Palmer, Alaska.

“I truly believe these things can measure any significant tsunami wave in the ocean,” said Fralick.

The original six DART buoys were placed in late 1990s, said Meinig. But they didn’t become fully operational until late 2003. Shortly after, one of the buoys detected a tsunami of only a few inches created by an earthquake near the Aleutian Islands in Alaska. That information helped the Pacific Tsunami Warning Center to decide there was no reason to issue a warning for Hawaii.

“That saved millions of dollars,” said Delores Clark, spokesperson for NOAA, because it prevented the need for evacuating millions of Hawaiians unnecessarily.

The DART technology came about because of a galvanizing event, said Meinig. In 1992, a 7.2 earthquake in California generated a tsunami that killed no one. But it raised concerns that a bigger earthquake could produce life-threatening tsunamis along the west coast. Congress asked NOAA to assess tsunami awareness and preparedness of the west coast. The agency approached scientists at the Pacific Marine Environmental Laboratory to design a system to detect tsunamis in the Pacific. The scientists created DART, then transitioned it to SAIC, which now owns the technology, said Fralick.

Five tsunami warning systems exist around the globe. They are located in the United States, Japan, Russia, French Polynesia and Chile.

The Pacific Tsunami Warning Center was created in 1949 following a 1946 tsunami that devastated a town in Hawaii, said Clark. The center in Alaska was set up in 1965 following an earthquake that measured more than 9 on the Richter scale, she said.

These warning centers monitor the pressure sensor data recorded by the DART buoys and transmit tsunami bulletins when appropriate. States affected by the bulletins then alert local authorities who then evacuate coastal areas.

“It’s up to the county and local communities to determine how they’re going to notify the public. Some have sirens; some have other methods,” said Wilson. He said a senate bill in the Oregon state legislature has proposed a uniform siren signal to be coordinated among the local authorities along the state’s coastline.

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