Image: Unknown, Courtesy of NOAA
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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9 Comments
Add CommentThe link in the 4th paragraph shows that the title of "biggest quake" depends on whether you're talking about magnitude, economic damage or lethality. the #3 quake in terms of magnitude (the 26Dec2004 Sumatra quake) was deadlier than the other "top 9" COMBINED. And the 15Jan2010 Haiti quake may have been even deadlier, despite not even making the magnitude top 10 at a mere 7.0.
Reply | Report Abuse | Link to thisMadscientist...true.
Reply | Report Abuse | Link to thisAn earthquake is a physical phenomemon independent of it's impact on people or the environment.
A .22 bullet can be more lethal than a nuclear blast. There are many variables involved. The 'biggies' in North America will likely come off the Alaska coast...not good for any locals but unlikely to cause much havoc in the greater scheme of things. A 7.5 in the Los Angeles region could be relatively benign or completely destroy the city...again, other variables involved.
A 7.5 from the New Madrid fualt system would dwarf anything in the LA area.
Reply | Report Abuse | Link to thisMagnitude grows via exponents. The mass of Europa is 4.80×10^22. So a 5.8 to a 6.8 earthquake grows by an exponential factor of 33. That is an awful lot of energy! And to think I live next door to a super cool underground volcano!
Reply | Report Abuse | Link to thisImagine the size of quakes if the Yellowstone caldera erupts. I would imagine earthquakes over 10.0 and possibly off the scale.
Reply | Report Abuse | Link to thisThe circular historic sizes and dates of earthquakes is very graphic. It would be interseting to see the present theoretical explanations of the progression of quakes, showing the forces and strains that are involved in subduction quakes and surface quakes. The main article is very good for a general appreciation of what earthquakes is all about. Thank you.
Reply | Report Abuse | Link to thisWouldnt a sixties 9.5 earthquake be an 8.5 today, after they downgraded the figures in the last decade or so.
Reply | Report Abuse | Link to thisSorry I cant be more exact.
theories predict that if yellowstone errupts, the ash cloud would certainly eliminate the human race. the quake caused by it WOULD be somewhere in the 7-10 magnitude range, but volcanoes usually have less energy release than a subduction zone quakes. the energy release would be great, yes, but the debris and dust cloud is what would cause the loss of sunlight and quality air, this would be an absolute devastation to the people of the entire world.
Reply | Report Abuse | Link to thiswhat makes you think they changed the scale? there are many ways to measure seismic activity, many different factors apply to each... but they have always been constant in how each scale measures seismic activity. the public uses the magnitude scale... again, not changed, and was developed in the early 1900s if not earlier by Richter, a Californian Seismologist.
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