Tsunami-Causing Earthquake Trimmed Bulge off Earth's Middle
By Michael Schirber
LiveScience Staff Writer
posted: 12 January 2005
06:21 am ET
The Dec. 26 earthquake off the coast of Indonesia was the fourth
largest in one hundred years. Scientists have determined that this
major shift in the Earth’s plates changed the planet’s shape – enough
to shorten the day by fractions of a second and to shift the North
Pole by an inch.
The general shape of the Earth is slightly oblate – that is, it is not
a perfect sphere but is slightly squished down, making it about 26
miles wider at the equator than between the poles. This shape,
however, is not rigid, with climate being a major distorting force.
But the magnitude nine earthquake last month almost certainly altered
the shape as well. Recent calculations have estimated that this
catastrophic land displacement caused a small reduction in the bulge,
making the planet more round.
“The waistline was reduced by not quite a millimeter because of the
earthquake,” said Benjamin Fong Chao from NASA’s Goddard Space Flight
Center.
This slimming down sped up the rotation of the Earth, much like when a
spinning ice skater pulls in her arms to increase her speed. The
length of the day correspondingly decreased by 2.68 millionths of a
second.
No watches need to be changed because of this. In fact, Chao told
LiveScience in a telephone interview that this change is too small for
current detection methods. But, he said, the change in the Earth’s
shape and pole location might be observable, once all the relevant
data is reviewed.
Crash Diet
Chao and his colleague, Richard Gross of NASA’s Jet Propulsion
Laboratory, have analyzed seismological data from 20,000 earthquakes
with magnitudes greater than five. They have modeled how each has
affected the shape of the Earth, and subsequently the rotation.
In two thirds of the cases, the planet has become less oblate, or
skinnier, following a temblor. The other one third of the time, the
planet has become more oblate.
None of these changes, however, were big enough to directly measure –
until maybe now.
“The Earth got hit pretty hard on December 26,“ Chao said. “For the
first time, we hope to see the effect of an earthquake, but it will
take a couple of months to sort through the data.”
The Earth’s profile can be measured with satellite laser ranging
(SLR). By precisely tracking the orbit of a satellite, scientists can
infer the gravitational pull from that part of Earth below the
satellite.
“We measure the gravity change, and from that, we infer the shape
change,” said Minkang Cheng from the University of Texas at Austin.
Seeing the effect of the earthquake, though, will be difficult because
there are other processes that cause greater distortions.
Cheng and his co-worker, Byron D. Tapley, have analyzed 28 years of
SLR data, identifying several cyclical patterns in the variations of
the Earth’s oblateness, which they have correlated with weather and
climate changes.
The amplitudes of these cycles are 10 times bigger than the expected
change from the earthquake.
“There’s no question that a signal [from the earthquake] is there in
the satellites, but it is very tough to separate this from the
climate-induced signal,” Tapley said.
The Weight of Water
One of the largest variations in the SLR data is a seasonal
“breathing” in and out. On average, the Earth’s shape fluctuates by
2.38 centimeters over the course of a year, Cheng said.
The cause of this annual shift is the redistribution of water.
Evaporation over the ocean leads to precipitation over land, which
eventually makes its way back to the ocean. Major climate changes can
alter this water cycle.
“The magnitude of that mass transport of water varies from year to
year.” Tapley said. “The change is very dramatic in El Nino years.”
Cheng and Tapley found that every 4-6 years the Earth becomes slightly
more oblate – by about 0.7 centimeters – due to the redistribution of
precipitation caused by an El Nino event.
“Essentially, El Nino puts more moisture in the lower latitudes,”
Tapley said.
Tapley and Cheng plan to look at how other climate changes –
specifically global warming – may affect the Earth’s shape in their
next paper.
The Weight of Ice
There is one other interesting variation in the SLR data due to the
effects of the last ice age, called the postglacial rebound (PGR).
Ten thousand years ago, when parts of the continents were covered in
ice, that weight deformed the earth by squeezing down on the poles.
When the ice melted, the land did not immediately pop back into place
but is even now still recovering.
That recovery has the Earth becoming less and less oblate – at a rate
of about a tenth of a centimeter per year, according to Cheng.
Chao said that the PGR also shifts the direction of the North Pole by
about four inches a year. Since this is only four times bigger than
the expected shift from the earthquake, Chao believes this is the best
hope for measuring the earthquake’s effect.
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| User: "tw" |
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| Title: Re: Tsunami-Causing Earthquake Trimmed Bulge off Earth's Middle |
27 Apr 2005 07:35:03 AM |
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<itwill@happen.com> wrote in message
news:1114605109.08eec5c172858774ff087ae2c4df5405@teranews...
Tsunami-Causing Earthquake Trimmed Bulge off Earth's Middle
Are you hoping for an internal tsunami to trim the bulge off your middle
(and the two bulges on your chest), Bitchtits?
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| User: "Henning Larsen" |
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| Title: Re: Tsunami-Causing Earthquake Trimmed Bulge off Earth's Middle |
27 Apr 2005 12:25:22 PM |
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"tw" <no@no.com>, wrote in alt.prophecies.nostradamus, on, 27 apr 2005 12:35:03 GMT:
<itwill@happen.com> wrote in message
news:1114605109.08eec5c172858774ff087ae2c4df5405@teranews...
Tsunami-Causing Earthquake Trimmed Bulge off Earth's Middle
Are you hoping for an internal tsunami to trim the bulge off your middle
(and the two bulges on your chest), Bitchtits?
Perhaps some hiccups will help?
--
H.
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| User: "" |
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| Title: Re: Tsunami-Causing Earthquake Trimmed Bulge off Earth's Middle |
28 Apr 2005 11:20:33 AM |
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Tommy The Homosexual Clown wrote:
<itwill@happen.com> wrote in message
news:1114605109.08eec5c172858774ff087ae2c4df5405@teranews...
Tsunami-Causing Earthquake Trimmed Bulge off Earth's Middle
Are you hoping for an internal tsunami to trim the bulge off your middle
(and the two bulges on your chest), Bitchtits?
Keep me out of your wierd fantasies.
Tony
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| User: "tw" |
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| Title: Re: Tsunami-Causing Earthquake Trimmed Bulge off Earth's Middle |
29 Apr 2005 02:47:46 AM |
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<itwill@happen.com> wrote in message
news:1114705098.ab71f9562d4bb85710637fbc59c68cec@teranews...
Tommy The Homosexual Clown wrote:
<itwill@happen.com> wrote in message
news:1114605109.08eec5c172858774ff087ae2c4df5405@teranews...
Tsunami-Causing Earthquake Trimmed Bulge off Earth's Middle
Are you hoping for an internal tsunami to trim the bulge off your middle
(and the two bulges on your chest), Bitchtits?
Keep me out of your wierd fantasies.
Talking of which:
Tony wrote in:
1114529613.a674c6b8818433ac753505fca2233454@teranews
"You're a fucking clueless Euro who sits in the stand watching a group
of men running around after a ball on a huge field while you pee on
each other instead of walking to a rest room, and you've got the gaul
to talk about American sports fans?"
(Note amusing misspelling of "gall")
Tony
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| User: "Shirley" |
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| Title: Re: Tsunami-Causing Earthquake Trimmed Bulge off Earth's Middle |
27 Apr 2005 03:18:24 PM |
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<itwill@happen.com> wrote in message
news:1114605109.08eec5c172858774ff087ae2c4df5405@teranews...
Tsunami-Causing Earthquake Trimmed Bulge off Earth's Middle
By Michael Schirber
LiveScience Staff Writer
posted: 12 January 2005
06:21 am ET
Confirms what I was telling you years ago Tony - middle age spread isn't
inevitable!
Shirley
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| User: "" |
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| Title: Re: Tsunami-Causing Earthquake Trimmed Bulge off Earth's Middle |
28 Apr 2005 11:21:21 AM |
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Shirley wrote:
<itwill@happen.com> wrote in message
news:1114605109.08eec5c172858774ff087ae2c4df5405@teranews...
Tsunami-Causing Earthquake Trimmed Bulge off Earth's Middle
By Michael Schirber
LiveScience Staff Writer
posted: 12 January 2005
06:21 am ET
Confirms what I was telling you years ago Tony - middle age spread isn't
inevitable!
Shirley
You're alive? ;-)
Tony
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| User: "MillKa!!!" |
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| Title: Re: Tsunami-Causing Earthquake Trimmed Bulge off Earth's Middle |
28 Apr 2005 03:39:16 AM |
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Your missing the "Bigger Picture" here.
Although 'astronomical' by current world standards, this was Major Shift requires a
balancing act of similar proportion You are totally dis-regarding the 'repercussions"
of a T-plate shift that could be a 10x of this magnitude.
Something will eventually have to shift to bring up the 'slack' created by this
'upheaval's!!!!
Just A Thought.
Have A CONCERNED Day. :-(]
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