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Author Topic: Japans quake moved the earth on its axis...but how?  (Read 5327 times)

Offline yamo

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From CNN:  Reports from the National Institute of Geophysics and Volcanology
 in Italy estimated the 8.9-magnitude quake shifted the planet on its axis
 by nearly 4 inches (10 centimeters).

Did it change the tilt?  Did it revolve the earth around its axis?  Will this impact seasonal weather patterns?  What other impact might this have?


 

Offline JimBob

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Japans quake moved the earth on its axis...but how?
« Reply #1 on: 12/03/2011 21:21:57 »
It is all due to centrifugal force. Along the fault plane where the earth moved, the total length of the crust became shorter by 35 cm. This results in a mass redistribution of the crust of several billions of pounds of rock.

Consider a ice skater spinning around. If their arms go out, they spin slower, if they pull their in, they spin faster. A shortening of the crust is like pulling your arms in while spinning - the earth spins faster.

BUT - this shortening did not occur at the equator so it will result in a slight - VERY slight - wobble that over time will cause the axis of the earth to adjust to the new condition.

The kicker is this - the earth is constantly changing in shape and we will never see this exact calculated change because there are earthquakes, and thus mass movement of the earth 's crust, that continually change the mass distribution of the earth system.

The earth is a dynamic, ever-changing system. It is never the same from day-to-day. Or century-to-century.
 

Offline FuzzyUK

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Japans quake moved the earth on its axis...but how?
« Reply #2 on: 12/03/2011 22:46:15 »
From CNN:  Reports from the National Institute of Geophysics and Volcanology
 in Italy estimated the 8.9-magnitude quake shifted the planet on its axis
 by nearly 4 inches (10 centimeters).

Did it change the tilt?  Did it revolve the earth around its axis?  Will this impact seasonal weather patterns?  What other impact might this have?

We had all that hype about the earth's axis shifting and associated day shortening to the tune of a few microseconds at the time of the 2004 tsunami event. It turns out that it's based on sheer mathematical ESTIMATION and satellites have not managed to measure any detectable shift. Variations in shift can be also be caused by volcanic and tidal effects from the moon.

Check this article on the Chilean earthquake which raises some of the issues you are concerned about:
http://news.nationalgeographic.com/news/2010/03/100302-chile-earthquake-earth-axis-shortened-day/

"Currently, scientists can measure the length of an Earth day with an accuracy of only about 20 millionths of a second, so the shortened day caused by the Chile earthquake can be estimated but not measured."


Basically it means stop worrying; the world will carry on as normal.
« Last Edit: 12/03/2011 22:57:57 by FuzzyUK »
 

Offline JimBob

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Japans quake moved the earth on its axis...but how?
« Reply #3 on: 15/03/2011 20:27:17 »
From Google News - http://www.google.com/hostednews/afp/article/ALeqM5jD4grYzpCUcbInAhd32dFS9TcooQ?docId=CNG.bd57fdfbae452af0d2b556455b5b59ec.191

Quake moved Japan by 8 feet: USGS

(AFP) – 3/13/2011

WASHINGTON — Japan's recent massive earthquake, one of the largest ever recorded, appears to have moved the island by about eight feet (2.4 meters), the US Geological Survey said.

"That's a reasonable number," USGS seismologist Paul Earle told AFP. "Eight feet, that's certainly going to be in the ballpark."

Friday's 8.9 magnitude quake unleashed a terrifying tsunami that engulfed towns and cities on Japan's northeastern coast, destroying everything in its path in what Prime Minister Naoto Kan said was an "unprecedented national disaster."

The quake and its tectonic shift resulted from "thrust faulting" along the boundary of the Pacific and North America plates, according to the USGS.

The Pacific plate pushes under a far western wedge of the North America plate at the rate of about 3.3 inches (83 millimeters) per year, but a colossal earthquake can provide enough of a jolt to dramatically move the plates, with catastrophic consequences.

"With an earthquake this large, you can get these huge ground shifts," Earle said. "On the actual fault you can get 20 meters (65 feet) of relative movement, on the two sides of the fault."

He said similar movements would have been seen for Chile and Indonesia.

In December 2004, a 9.1 magnitude quake off Sumatra caused a tsunami that killed an estimated 228,000 people. An 8.8 quake off the coast of Chile in February 2010 killed more than 500.

There was not a similar ground shift in the 7.0 earthquake that devastated Haiti in February 2010, Earle said.

"A magnitude 7.0 is much smaller than the earthquake that just happened in Japan," he said. "We've had aftershocks (in Japan) larger than the Haiti earthquake."

Kenneth Hudnut, a USGS geophysicist, said experts read data including from global positioning systems to determine the extend of the shift.

"We know that one GPS station moved (eight feet), and we have seen a map from GSI (Geospatial Information Authority) in Japan showing the pattern of shift over a large area is consistent with about that much shift of the land mass," he told CNN.

 

Offline Geezer

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Japans quake moved the earth on its axis...but how?
« Reply #4 on: 15/03/2011 20:40:19 »
It is all due to centrifugal force...


No it ain't! There ain'ta no sanity clause, and there ain'ta no no centrifugal force either.

Maybe you meant "centripetal force"?
 

Offline JimBob

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Japans quake moved the earth on its axis...but how?
« Reply #5 on: 15/03/2011 21:09:36 »
Jes hold on there, you old coot.

Bach wrote a whole lot of them thar centrifugal thingies. Ever heard of the music of the spears? That's what this is all about!
« Last Edit: 15/03/2011 23:52:43 by JimBob »
 

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Japans quake moved the earth on its axis...but how?
« Reply #5 on: 15/03/2011 21:09:36 »

 

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