HONOLULU — Scientists have developed an underwater tsunami-detection system aimed at warning people in shoreline areas several hours in advance that a deadly ocean wave is headed for land.

Nestled strategically on the ocean floor at depths of up to 18,000 feet, the five recently developed devices are intended to give people on the West Coast and in Hawaii more time to head for higher ground.

Since 1990, 10 major tsunamis in the Pacific have killed more than 4,000 people.

Of the five devices already deployed, three are off the Aleutian Islands Chain in Alaska, one off Vancouver, British Columbia, and one off Oregon.

A sixth device will be lowered to the ocean floor near the Equator between Chile and Hawaii in the next few weeks, said Eddie Bernard of the National Oceanic and Atmospheric Administration in Seattle.

The instruments use sonic chirps to send data to a surface buoy, which relays them to a satellite and system computers.

"This is a giant step in technology" from the time that tsunami warnings were based on the size and location of the earthquake and a network of tide stations located in harbors and bays around the Pacific, Bernard said.

The instruments also could detect tsunamis generated by coastal or subsurface landslides that wouldn't be noticed by seismographs recording earthquakes, he said.

"It could even be created by a meteor hitting the ocean," Bernard said.

Scientists suspect an earthquake-triggered tsunami that killed more than 2,000 people in Papua New Guinea in 1998 was bolstered by an undersea landslide.

Hawaii's worst experience in modern times came in 1946 when the April Fool's Day tsunami generated by an earthquake in the Aleutian Islands sent a 25-foot-high wall of water ashore, killing 173 people, mostly in Hilo. On May 23, 1960, a tsunami that hit Hilo killed 61 people.

Bernard wants the system to eventually have 10 of the devices, each of which cost about $250,000 to build and maintain. He also is trying to get Japan to deploy detectors.

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The devices also can tell officials that a tsunami has not been generated, saving millions of dollars in economic losses resulting from unnecessary evacuations.

In October 1995, a major earthquake near Japan prompted tsunami warning sirens throughout Hawaii. Although the wave never reached here, the daylong shutdown of the islands during evacuation of coastal areas cost the state's economy an estimated $30 million.

Avoiding false alarm evacuations along the West Coast would justify the $2.3 million annual cost of the system, which scientists ultimately hope will help save lives.

"If I can save one life with this system, it was worth it," Bernard said.

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