Monday, May 28, 2012

The Biggest Earthquakes Since 1900, Measuring Quakes Video

Just How Big Was the Biggest Earthquake?

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. So we got to thinking about earthquakes.

Chile May 23, 1960
The worlds tectonic plates are primed for activity, evidenced by the Japanese quake, the unusual Virginia Quake and the increased global activity. That being said, we are just entering the 11 year peak solar cycle and we are now told that Planet X is cruising through our neighborhood making other planets wobble. On top of all that, it is after all 2012.

If you are like we are than you know that a magnitude 8.0 quake it exponentially larger than a magnitude 7.0 quake but exactly by how much? What does it mean and what can we expect. Also it should be noted that not all of the largest earthquakes are the most deadly, there are factors at play in every earthquake. Keep in mind when seismologist talk about the size of an earthquake they are only talking about the physical phenomenon independent of it's impact on people or the environment.

Terminology is important when talking earthquakes, the Sumatra Quake that comes in at number three in terms of magnitude, 9.1, was deadlier than the other top nine quakes combined. The Haiti Quake at 7.0, not even making the top 20 may have been the deadliest quake on record. The jury is still out and it will be some time before we know the full scale of that earthquake. 

So there are many different ways to look at a quake, obviously the physical aspect (whether it is a 7.0 or 8.0) is important but there is also loss of life and economic impact. As one of the people commenting on this article  points out, a 22 caliber bullet could potentially be more lethal than a nuclear bomb, depending on where you are and your circumstances.

Largest Earthquakes on Record Since 1900


LocationDate UTCMagnitudeLat.Long.
1.Chile1960 05 229.5-38.29-73.05Kanamori, 1977
2.Prince William Sound, Alaska1964 03 289.261.02-147.65Kanamori, 1977
3.Off the West Coast of Northern Sumatra2004 12 269.13.3095.78Park et al., 2005
4.Near the East Coast of Honshu, Japan2011 03 119.038.322142.369PDE
5.Kamchatka1952 11 049.052.76160.06Kanamori, 1977
6.Offshore Maule, Chile2010 02 278.8-35.846-72.719PDE
7.Off the Coast of Ecuador1906 01 318.81.0-81.5Kanamori, 1977
8.Rat Islands, Alaska1965 02 048.751.21178.50Kanamori, 1977
9.Northern Sumatra, Indonesia2005 03 288.62.0897.01PDE
10.Assam - Tibet1950 08 158.628.596.5Kanamori, 1977
11.Off the west coast of northern Sumatra2012 04 118.62.31193.063PDE
12.Andreanof Islands, Alaska1957 03 098.651.56-175.39Johnson et al., 1994
13.Southern Sumatra, Indonesia2007 09 128.5-4.438101.367PDE
14.Banda Sea, Indonesia1938 02 018.5-5.05131.62Okal and Reymond, 2003
15.Kamchatka1923 02 038.554.0161.0Kanamori, 1988
16.Chile-Argentina Border1922 11 118.5-28.55-70.50Kanamori, 1977
17.Kuril Islands1963 10 138.544.9149.6Kanamori, 1977
Updated 2012 April 11
The colossal 9.5 quake in Chile and the powerful tsunami that followed killed more than 1,400 people and left 2 million homeless. 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 mega-thrust 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. 

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.

video

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. Fiddling with any of those factors will change the magnitude.

Power limits
Yet some earthquakes are, by the mechanism that causes them, able to unleash far more power than others. All the most powerful earthquakes on record are so-called subduction earthquakes — the sort that happen where tectonic plates overlap.

And that's because they simply have more real estate at their disposal than earthquakes that happen in the middle of a continental plate, known as strike-slip earthquakes.

These earthquakes happen along faults that are, essentially, vertical — the San Andreas Fault is perhaps the most famous such fault in the United States.

The faults that produce strike-slip quakes plunge into the Earth's interior in a fairly straight line. That means they reach hotter, gooier geological territory — places where the rocks aren't rigid enough to make an earthquake — faster than the faults at subduction zones, which head into the Earth at an angle.

"If you go straight down, you get to the non-brittle zone faster than if you go at an angle," Earle said. And that means strike-slip faults just don't have as much area as the angled faults at subdcution zones, and thus can't produce quakes with quite as much punch.

Yet strike-slip quakes can still cause catastrophic damage. And scientists are hard at work on designing systems that will provide a few seconds of warning when an earthquake hits, no matter what the mechanism that caused it.



Predicting Earthquakes 
Predicting these events seems to be a fools errand, the world's best seismologist have studied, ground pressure, moon phase, sun spots, fluids in the ground, pressure buildup, magnetic charges and not one of them (at least yet) correlates to how, why and where earthquakes will happen.

Nothing can predict an earthquake better than the common toad (Bufo bufo) which can predict seismic activity almost five days in advance.  A 2010 study published in Journal of Zoology found that 96 percent of male toads in a population abandoned their breeding site five days before the earthquake that struck L'Aquila, Italy, in 2009, about 46 miles (74 kilometers) away. Researchers aren't quite sure how the toads do this, but it's believed that they can detect subtle signs, such as the release of gases and charged particles, that may occur before a quake [source: Science Daily]. 

So if earthquakes can't be predicted than the only option is to prepare! 


Earthquakes, How Big, Where, When, What to Expect
Thanks to Scientific America

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