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Explainer: Why Chile's Quake Wasn't
Unexpected
By BRYAN WALSH Saturday, Feb. 27, 2010
The Pacific's volatile Ring of Fire region produces most of the world's earthquakes and volcanic
eruptions, including this one a few hundred miles south of Santiago, Chile, photographed
spewing lava in 2009.
AFP / Getty Images
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Scientists still can't predict exactly when earthquakes will occur, but the massive temblor that
struck off the coast of Chile early Saturday was anything but unexpected. Chile sits on the Ring
of Fire, the volatile, 40,000 km-long (25,000 MILE) zone that encircles the Pacific Ocean and
includes the most seismically dangerous ground on the planet. The unstable plate tectonics
along the Ring produce some 90% of the world's earthquakes as well as most of its volcanic
eruptions. (See where experts predict the next five major earthquakes will be.)
Because the Ring follows the coastlines of Pacific Ocean, almost any major quake can also
produce a tsunami, a powerful wave that travels from the epicenter of the temblor across the
ocean basin. That's what happened in 2004, when a 9.3-magnitude quake off the Indonesian
island of Sumatra triggered a devastating tsunami, and that's is what's likely to happen following
today's 8.8-magnitude quake off the coast of Chile. (See the latest photos of the
earthquake in Chile.)
Temblors in the Ring of Fire are so common that a 7.0-magntitude quake hit Japan's Ryuku
Islands yesterday. Today's Chilean quake occurred on one of the more powerful fault lines in
the region, where the underwater Nazca Plate in the Pacific gradually submerges beneath the
westward moving South American plate. The border between these two plates is known as a
thrust fault, and the sudden rubbing of the plates against each other resulted in an earthquake
that ripped across an estimated 400 miles of the fault. With a Richter scale magnitude of 8.8,
the Chilean quake was nearly 1,000 times stronger than the temblor that hit Haiti last month.
Chile, however, is no stranger to major earthquakes. In 1960, a 9.5-magnitude temblor — the
strongest quake ever recorded by scientific instruments — hit the Chilean city of Valdivia, killing
nearly 2,000 people. And although today's quake is the strongest in the last half-century to hit
Chile, the country has had 13 quakes of 7.0 or higher on the Richter scale since 1973. That
geologic history helps explain why building codes are far tougher in Chile than they are in Haiti,
which should help limit the number of casualties from today's quake. So far, 147 people have
been confirmed dead, but that number is expected to rise. (Read "After Chile's Quake:
Waiting for a Tsunami on Waikiki")
Because the quake occurred offshore, however, the destruction likely won't be limited to Chile.
As the underwater plates shake, they push the water above them up, creating the beginning of a
wave, not unlike dropping a stone in a bathtub. The wave then travels away from the epicenter
of the quake. In the case of the Chile temblor, the waves are moving in a northwest direction
across the Pacific, putting nearly every shoreline along the ocean at some risk.
In open water, a tsunami makes barely a ripple, but as the waves approach a shoreline, they
gather strength and height, finally spilling over land.
The waves travel at roughly the speed of a passenger jet, but because of the vast distance they
are traveling across the Pacific from Chile's coast, vulnerable islands hours to prepare. That
wasn't the case during the 2004 tsunami, which rippled across the much smaller Indian Ocean
basin before there was time to raise a proper warning.
Hawaii, which sits squarely in the middle of the potential tsunami's path, also has a
sophisticated warning protocol that should get people off the shore in time. By contrast,
Indonesia, Sri Lanka and Thailand, the areas hardest hit by the 2004 tsunami, had virtually no
alert system.
The fact that the Chilean quake occurred six weeks after the catastrophic temblor in Haiti could
lead many to wonder if we're entering a new era of seismological disaster. But the two quakes
are unrelated, occurring on different faults. The reality is that Chileans live in one of the most
seismically dangerous regions in the world, and an earthquake as powerful as the one that hit
this morning was just a matter of time. The question is how Chileans — and the rest of the world
— can better prepare for geological calamity.
Read more: http://www.time.com/time/world/article/0,8599,1968527,00.html#ixzz1dOXUAzSJ
What is the Pacific Ring of Fire?
2.) What event can be triggered by an Earthquake?
a. Tornado
b. Hurricane
c. El Nino
d. Tsunami
3.) Why are Chileans mentally prepared for Earthquakes?
1.)