Just How Big Was the Biggest Earthquake?

Image: Unknown, Courtesy of NOAA

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This week marks the anniversary of the largest earthquake ever recorded ? a magnitude-9.5 earthquake that ripped along the coast of southern Chile on May 22, 1960.

The colossal quake and the powerful tsunami that followed killed more than 1,400 people and left 2 million homeless in Chile. And its devastation reached far beyond South America.

The tsunami swept across the Pacific Ocean, wreaking havoc in Hawaii, the Philippines and Japan; a day after the earthquake, walls of water up to 18 feet (5.5 meters) high rushed ashore at Honshu, Japan's main island, destroying 1,600 homes and killing 138 people.

The colossal quake was what is known as a megathrust earthquake. These giant quakes, the most powerful quakes the planet is capable of unleashing, occur along subduction zones, where one tectonic plate dives beneath another. [The 10 Biggest Earthquakes in History]

In this case, the quake was caused when a 620-mile-long (1,000 kilometers) stretch of the Nazca plate, an oceanic plate that forms a large swath of the Pacific Ocean floor, lurched deeper beneath the South American plate, producing the only 9.5-magnitude quake on record.

So just how big is a 9.5? An earthquake magnitude video, created with an animation from Nathan Becker, an oceanographer at the Pacific Tsunami Warning Center, offers a simple way to understand the vast differences between one magnitude and the next.

Essentially, each successive magnitude is 33 times larger than the last. That means a magnitude-8.0 earthquake is 33 times stronger than a 7.0, and a magnitude-9.0 earthquake is 1,089 (33 x 33) times more powerful than a 7.0 ? the energy ramps up fast.

Magnitude measures
Although figuring out an earthquake's power requires lots of complicated math and lots of data, magnitude boils down to three basic factors: area, distance and friction.

"It's about the physical properties of the fault," said Paul Earle, a seismologist with the U.S. Geological Survey.

To get the magnitude, Earle told OurAmazingPlanet, you multiply the area of the fault that slipped ? how much real estate moved ? by the distance it moved and by the amount of friction on the fault.

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