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Kai Ryssdal: Even before the shaking started, millions of people in Tokyo knew this quake was coming. Japan has spent hundreds of millions of dollars over the past 15 years building an earthquake early-warning system. Today the investment may have paid off.
Marketplace's Steve Henn reports.
Steve Henn: More than a minute before the ground began to shake in Tokyo, texted warnings hit millions of cell phones; stations interrupted their broadcasts; bullet trains came to a halt; and factories got urgent e-mails to secure their assembly lines.
It was Japan's earthquake early-warning system.
Peggy Hellweg: I am certain the system saved lives today.
Dr. Peggy Hellweg is a seismologist at UC Berkeley. She says you can't predict quakes but you can warn people that one's coming.
Hellweg: There are different kinds of waves that are radiated from an earthquake -- the P waves are primary, they come first, and they travel faster than the S waves.
But S waves do the damage. So Japan's deployed thousands of sensors that detect fast-moving P waves. When sensors detect a quake, computers calculate its size and then broadcast warnings across the country. Today, that entire process took 8.6 seconds.
David Oppenheimer: The Japanese have been ahead of the game.
David Oppenheimer at the U.S. Geological Survey.
Oppenheimer: After the Kobe earthquake, they spent something on the order of $500 million to install modern seismic equipment in their country.
Those investments started in 1995 and the system went live in 2007.
Today the U.S. is developing a similar early warning system for the west coast. Oppenhiemer says it at least five years and tens of millions of dollars away.
From Silicon Valley, I'm Steve Henn for Marketplace.