Tsunami detectors offer time to head for higher ground

Posted: Thursday, August 23, 2001

HONOLULU -- It's not a matter of if. It's more a matter of when and where.

At some point a major earthquake will launch the next invisible tsunami on a 500 mph charge across the Pacific Ocean to hammer and inundate coastal communities thousands of miles away.

The massive wave pent-up with millions of tons of water will rise higher and higher as the leading edge reaches the shallows, then spills with ground-shaking force, sweeping over property and humanity in low-lying coastal areas.

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

Now, a new submerged detection system aims to give people in shoreline areas more time to head for higher ground, increasing their chance of survival.

Nestled strategically on the ocean floor, at depths of up to 18,000 feet, are five recently developed tsunami detection devices. They are intended to give several hours warning that a deadly and destructive bulge on the ocean is headed for land as fast as a jumbo jetliner.

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

Data from the monitors are on the Internet, allowing people to watch as the system switches into emergency mode following an earthquake with minute-by-minute pressure readings that can determine if there is a tsunami.

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, director of the National Oceanic and Atmospheric Administration's Pacific Marine Environmental Laboratory in Seattle.

It will be the first real protection for Hawaii from the earthquake-prone coastal areas of South America, he said.

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

The array is located to provide early warning for the West Coast and Hawaii, but also will be helpful in alerting foreign coastal areas around the Pacific Rim, Bernard said.

The instruments also could detect tsunamis generated by coastal or subsurface landslides that wouldn't be detected 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.

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.

The first generation of monitors deployed in 1995 were imperfect and prone to failure, ''but we've worked out the bugs and finally have a good system in place'' with 98 percent reliability, he said.

The instruments, with backup transmission systems, use sonic chirps to send data to a surface buoy, which relays them to a satellite and then to 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.

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.

Comparable savings by avoiding false alarm evacuations along the West Coast would justify the $2.3 million annual cost of the system hundreds of times over.

On the other hand, correctly forecasting tsunamis will save lives.

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

The other part of the effort is to increase public awareness, especially along the West Coast, of the danger of tsunamis and the creation of tsunami hazard zones that would need to be evacuated, he said.

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.



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