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[Physltest] [Phys-L] Fwd: NASA Details Earthquake Affects on the Earth



<html>
Physics-L<br>
<x-tab>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</x-tab>I hate to
just forward things that are already genreaqlly out there but this was
discussed earlier.<br>
<x-tab>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</x-tab>Gary
<br>
<blockquote type=cite class=cite cite>Date: Mon, 10 Jan 2005 18:17:10
-0800<br>
From: NASA Jet Propulsion Laboratory &lt;info@jpl.nasa.gov&gt;<br>
Subject: NASA Details Earthquake Affects on the Earth<br>
<br>
<font face="Times, Times">Alan Buis (818) 354-0474<br>
</font><br>
<font face="Times, Times">Jet Propulsion Laboratory, Pasadena,
Calif.<br>
</font><br>
&nbsp;<br>
<br>
<font face="Times, Times">Gretchen Cook-Anderson/Dolores Beasley (202)
358-0836/1753<br>
</font><br>
<font face="Times, Times">NASA Headquarters, Washington, D.C.<br>
</font><br>
&nbsp;<br>
<br>
<font face="Times, Times">News Release:
2005-009&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
January 10, 2005<br>
</font><br>
&nbsp;<br>
<br>
<h1><font face="Times, Times"><b>NASA Details Earthquake Affects on the
Earth</b></font></h1><br>
<br>
&nbsp;<br>
<br>
<font face="Times, Times">NASA scientists using data from the Indonesian
earthquake calculated it affected Earth's rotation, decreased the length
of day, slightly changed the planet's shape, and shifted the North Pole
by centimeters. The earthquake that created the huge tsunami also changed
the Earth's rotation.<br>
</font><br>
&nbsp;<br>
<br>
<font face="Times, Times">Dr. Richard Gross of NASA's Jet Propulsion
Laboratory, Pasadena, Calif., and Dr. Benjamin Fong Chao, of NASA's
Goddard Space Flight Center, Greenbelt, Md., said all<br>
</font><br>
<font face="Times, Times">earthquakes have some affect on Earth's
rotation. It's just they are usually barely noticeable.<br>
</font><br>
&nbsp;<br>
<br>
<font face="Times, Times">&quot;Any worldly event that involves the
movement of mass affects the Earth's rotation, from seasonal weather down
to driving a car,&quot; Chao said.<br>
</font><br>
&nbsp;<br>
<br>
<font face="Times, Times">Gross and Chao have been routinely calculating
earthquakes' effects in changing the Earth's rotation in both
length-of-day as well as changes in Earth's gravitational field. They
also study changes in polar motion that is shifting the North Pole. The
&quot;mean North pole&quot; was shifted by about 2.5 centimeters (1 inch)
in the direction of 145 degrees East Longitude. This shift east is
continuing a long-term seismic trend identified in previous
studies.<br>
</font><br>
&nbsp;<br>
<br>
<font face="Times, Times">They also found the earthquake decreased the
length of day by 2.68 microseconds.&nbsp; Physically this is like a
spinning skater drawing arms closer to the body resulting in a faster
spin. The quake also affected the Earth's shape. They found Earth's
oblateness (flattening on the top and bulging at the equator) decreased
by a small amount. It decreased about one part in 10 billion, continuing
the trend of earthquakes making Earth less oblate.<br>
</font><br>
&nbsp;<br>
<br>
<font face="Times, Times">To make a comparison about the mass that was
shifted as a result of the earthquake, and how it affected the Earth,
Chao compares it to the great Three-Gorge reservoir of China. If filled,
the gorge would hold 40 cubic kilometers (10 trillion gallons) of water.
That shift of mass would increase the length of day by only 0.06
microseconds and make the Earth only very slightly more round in the
middle and flat on the top. It would shift the pole position by about two
centimeters (0.8 inch).<br>
</font><br>
&nbsp;<br>
<br>
<font face="Times, Times">The researchers concluded the Sumatra
earthquake caused a length of day change too small to detect, but it can
be calculated. It also caused an oblateness change barely detectable, and
a pole shift large enough to be possibly identified. They hope to detect
the length of day signal and pole shift when Earth rotation data from
ground based and space-borne position sensors are reviewed.<br>
</font><br>
&nbsp;<br>
<br>
<font face="Times, Times">The researchers used data from the Harvard
University Centroid Moment Tensor database that catalogs large
earthquakes. The data is calculated in a set of formulas, and the results
are reported and updated on a NASA Web site.<br>
</font><br>
&nbsp;<br>
<br>
<font face="Times, Times">The massive earthquake off the west coast of
Indonesia on December 26, 2004,<br>
</font><br>
<font face="Times, Times">registered a magnitude of nine on the new
&quot;moment&quot; scale (modified Richter scale) that indicates the size
of earthquakes. It was the fourth largest earthquake in one hundred years
and largest since the 1964 Prince William Sound, Alaska earthquake.<br>
</font><br>
&nbsp;<br>
<br>
<font face="Times, Times">The devastating mega thrust earthquake occurred
as a result of the India and Burma plates coming together. It was caused
by the release of stresses that developed as the India plate slid beneath
the overriding Burma plate. The fault dislocation, or earthquake,
consisted of a downward sliding of one plate relative to the overlying
plate. The net effect was a slightly more compact Earth. The India plate
began its descent into the mantle at the Sunda trench that lies west of
the earthquake's epicenter. For information and images on the Web,
visit:<br>
</font><br>
&nbsp;<br>
<br>
<div align="center">
<font face="Times, Times"><a href="http://www.kintera.org/TR.asp?ID=M66682115959476410898465";>http://www.nasa.gov/vision/earth/lookingatearth/indonesia_quake.html</a></font>
<font face="Times, Times">.<br>
</font></div>
<br>
&nbsp;<br>
<br>
<font face="Times, Times">For details on the Sumatra, Indonesia Earthquake, visit the USGS Internet site:<br>
</font><br>
&nbsp;<br>
<br>
<div align="center">
<font face="Times, Times"><a href="http://www.kintera.org/TR.asp?ID=M66682125959476410898465";>http://neic.usgs.gov/neis/bulletin/neic_slav_ts.html</a></font> <font face="Times, Times">.<br>
</font></div>
<br>
&nbsp;<br>
<br>
<font face="Times, Times">For information about NASA and agency programs Web, visit:<br>
</font><br>
&nbsp;<br>
<br>
<div align="center">
<font face="Times, Times"><a href="http://www.kintera.org/TR.asp?ID=M66682135959476410898465";>http://www.nasa.gov</a><a href="http://www.nasa.gov/";> </a> .<br>
</font></div>
<br>
<div align="center">
&nbsp;<br>
</div>
<br>
<font face="Times, Times">JPL is managed for NASA by the California Institute of Technology in Pasadena.<br>
</font><br>
&nbsp;<br>
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-end-<br>
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