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This summer, NPR has been looking into the science of waves - and today, seismic waves. They are especially relevant following the destruction of last week's earthquake in central Italy. The biggest earthquake ever recorded was in Chile, in 1960. The earth shook for 10 minutes, sending shock waves around the world. That quake helped scientists come up with today's tsunami and quake early warning systems. NPR's Rae Ellen Bichell reports.
RAE ELLEN BICHELL, BYLINE: The rumbling started on the afternoon of May 22, 1960. Sergio Barrientos was about 8 years old.
SERGIO BARRIENTOS: So I vividly remember what happened.
BICHELL: He was walking down a street in his hometown in southern Chile when the ground started to shake. He remembers electric wires swinging from the telephone poles.
BARRIENTOS: And at the same time, I saw some of the chimneys falling down through the roofs of the houses.
BICHELL: The ground was shaking so hard that Barrientos couldn't stay on his feet. He was stuck on the ground for several minutes as the earth heaved. Barrientos has since spent years studying earthquakes. He directs the National Seismological Center in Santiago, Chile. That earthquake in 1960 was the most powerful one ever recorded, with a magnitude of at least 9.5.
BARRIENTOS: It was a huge - a huge earthquake.
BICHELL: And he now knows that during the quake, while he was stuck on the ground, his hometown lurched west about 30 feet.
BARRIENTOS: The whole country stretched during this earthquake. That increased the area of the country itself.
BICHELL: The quake expanded the country by an area equal to about 1,500 football fields and caused a lot of destruction. It was a big news story at the time.
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UNIDENTIFIED REPORTER: Nations reckon up the grim toll of the seismic shocks that triggered a week of devastating earthquakes and volcanic eruptions in Chile and tidal waves and tropical storms that battered every shore, from the Philippines and Japan to Alaska.
BICHELL: The Great Chilean Earthquake revealed something new about the planet, that the world itself could vibrate like a guitar string. The waves went through every part of the globe, even its core. And because they were so strong, instruments from around the world picked up the signal. When it was done, seismologists realized that the earthquake had given them a window into the earth's structure, like giving the planet an ultrasound.
LARRY RUFF: That's very exciting because there's a new type of information that had not yet been available by all the studies from all the generations of seismologists before.
BICHELL: That's Larry Ruff, a seismologist at the University of Michigan. At the time, researchers were just starting to agree that the continents sat on top of giant plates and that earthquakes were caused as those plates folded into each other. They were also just realizing that big seismic waves, like the ones that Chile experienced, could actually lift the ocean floor, causing water to roll across the Pacific Ocean and crash into countries many hours later.
RUFF: And so it just caused an immediate flurry of activity.
BICHELL: Because people realized that if they just had the right instruments to pick up on those waves, they could warn people that a tsunami was headed their way.
RUFF: As soon as that happened, of course, it just prompted this huge new effort to have even better high-quality seismographs located all the way around the world.
BICHELL: Now those instruments make up a global tsunami warning system. But that doesn't mean another major earthquake would be any less destructive.
RUFF: We don't want to see an earthquake any larger than the 1960 earthquake, that's for sure.
BICHELL: But it could happen. Scientists think that an earthquake as big as the Great Chilean Earthquake could occur on a number of faults, including one along the northwest coast of the U.S. Rae Ellen Bichell, NPR News.
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