Imagine being alerted by cell phone that the ground under your feet will start shaking in 30 seconds.
Tokyo residents faced that situation just before their world turned upside down Friday.
The magnitude 9.0 earthquake that ruptured the seafloor off Japan was the first major test of the nation’s $1 billion investment in earthquake early-warning technology.
Similar systems could be installed in the Pacific Northwest and California, scientists say. All it takes is money — and a way to ensure the alerts do more good than harm.
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“It has to be a very clear message, and people have to know what to do with the information,” said John Vidale, director of the Pacific Northwest Seismic Network at the University of Washington.
The rising death toll in Japan underscores the limitations of a warning system. Alerts are most valuable to those in communities distant from the epicenter. For those near ground zero, like the Japanese coastal cities flattened by tsunami waves, there’s not enough time to sound the alarm.
Warnings would do Seattle little good in the case of a quake on the shallow fault that underlies the city but could benefit Olympia and other cities. But Seattle could have as much as five minutes’ warning of a coastal megaquake such as the one that rocked Japan and unleashed a deadly tsunami, Vidale said. Even 15 or 20 seconds can be enough time for people to dive under a table, for train operators to hit the brakes and for factories to shut down production lines, said Tom Jordan, director of the Southern California Earthquake Center.
“In my book,” he said, “every second counts.”
Along with the U.S. Geological Survey, Jordan and a consortium of colleagues have been fine-tuning and testing a prototype warning system in California for years. Rolling it out statewide would cost $100 million, he said.
The price tag for a system in Washington and Oregon, which face more powerful but less frequent quakes than California, would be about $50 million, Vidale estimates. Maintenance and monitoring would require an additional $6 million a year.
Those costs are small compared with the multibilliondollar toll of even a modest earthquake. But with the state budget in its current state, Washington is considering cuts to the existing seismicmonitoring program.
In Japan, where earthquake preparedness is woven into the fabric of life, the government spares little expense to protect its citizenry. “For every 10 seismic stations we buy, they buy a thousand,” Cal Tech geophysicist Egill Hauksson said.
Japan’s warning system is the most advanced in the world. A dense network of seismic instruments detect initial tremors generated by an earthquake. These so-called p-waves race through the earth but cause little damage. The warning is sounded in the interval before more destructive, but slower-moving, tremors called s-waves arrive.
As the frantic search for survivors continues in Japan, it’s too early to quantify benefits from the alert system. But the technology itself performed well, and the messages undoubtedly saved many lives, Jordan said.
Warnings that featured a countdown clock were broadcast via television, radio and cell phone eight seconds after the quake was first detected, Hauksson said.