Sumatran Quake Left 'Scar' on Earth's Gravity
Mon Apr 25, 5:24 PM ET
LiveScience Staff
LiveScience.com
The devastating 2004 Sumatran earthquake, which caused the worst
tsunami in modern times, should have left a detectable scar on Earth's
gravity field, European scientists said Monday.
A satellite planned for launch next year could detect the blemish,
they said.
The magnitude 9.3 earthquake has already been said to have shortened
the day by fractions of a second, shifted the North Pole by an inch,
and made the planet less fat around the middle.
The new prediction comes from Roberto Sabadini and Giorgio Dalla Via
at the University of Milan. The idea is fairly straightforward. The
strength of Earth's gravity varies depending on the depth of a trench
or height of a mountain, as well as the density of material. Even
changing tides alter the gravity field.
The Dec. 26, 2004 quake lifted an 18-foot (6 meter) ledge along a
620-mile (1,000 kilometer) fault.
Gravity variations are measured using the geoid, which is similar to
sea-level. The geoid is a hypothetical "surface" around the Earth at
which the planet's gravitational pull is the same everywhere. Over
dense areas, the geoid moves away from the real surface, and where
gravity is less, the geoid moves closer to the real surface.
The Sumatran quake, the geoid moved as much as 0.7 inches (18
millimeters), the scientists predict.
The variations in the gravity field are already studied from space
with NASA's GRACE mission.
The European Space Agency's Gravity Field and Ocean Circulation
Explorer (GOCE), planned to launch in 2006, is designed to be very
sensitive to minor differences. As the spacecraft passes over regions
of stronger and weaker gravitational pull, it will bob up and down.
A study of gravity scar data could in turn refine estimates of the
physical rupture of a fault.
"Seismology is good for detecting the slip of earthquake faults and
the location of the epicenter, geoid monitoring can determine how much
mass is actually being moved around," Sabadini said.
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| User: "" |
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| Title: Re: Tsunami Quake affected Earth's Gravity |
27 Apr 2005 05:00:12 PM |
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So what are the odds for another within 2 years?
LB
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| User: "=?iso-8859-1?q?There_are_now_only_2792_days_until_the_end_of_the_Mayan_Calendar=99?=" |
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| Title: Re: Tsunami Quake affected Earth's Gravity |
27 Apr 2005 10:38:18 PM |
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Try within 2 months, Mr Ballam !!!!!!
& I wouldn't want to be living in places such as Darwin, Broome or Port
Hedland when it occurs !!!!!
HOOROO
UNCLE WALLY
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