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The earth is always in motion. And as its mantle plates deep =
underground move=20
and shift, they groan, moan, pop and crack. But much of it happens so =
slowly =E2=80=94=20
just 5 to 7 centimeters a year =E2=80=94 that the sound has to be sped =
up and amplified=20
so that it can easily be heard by the human ear.
Sometimes, =
though, the=20
earth moves a lot faster, creating the large-scale devastation =
associated with=20
such natural disasters as the 2008 Sichuan earthquake in China or this =
year's=20
quake in L'Aquila, Italy.
Looking for answers by looking at =
the=20
earth's interior structure
Scientists still don't know why =
there are=20
earthquakes, says Stephen Gao. The seismologist has worked in Africa, =
China and=20
Siberia, and is currently heading a research team for EarthScope, =
in Rolla,=20
Missouri.
EarthScope is part of a huge project to =
seismographically map=20
the continental U.S. and Alaska. "The idea is to use 400 seismographs to =
cover=20
the whole U.S. in about 14 years," Gao explains, adding that the =
information=20
that will come from those monitors is designed to help scientists =
predict, not=20
prevent, earthquakes. "[But if] you can predict one, then you can do =
something=20
to lessen the damage caused by an earthquake," he points out. "People =
can come=20
out of their house and camp outside. You can shut down the power, the =
natural=20
gas lines. In that situation, you can reduce the damage a=20
lot."
EarthScope began putting down seismometers on the U.S. west =
coast=20
in 2002 and is moving its operations eastward across the country. The =
project is=20
currently entering the area of the New Madrid fault zone, in Missouri =
and=20
several nearby states. It's the site of one of the most powerful =
earthquakes=20
ever recorded in North America.
Finding the right locations =
for=20
monitoring movement
The placement of the 400 seismometers is=20
critical. To ensure complete coverage they are being laid out on a =
massive grid,=20
with stations about 70 kilometers apart. Because the instruments are =
highly=20
sensitive, they can't be too close to roadways or large trees. Both give =
off=20
vibrations that could create false readings. So, here in Missouri, open =
cow=20
pastures and hay fields are the best locations.
Gao has enlisted =
the=20
help of four students to identify possible seismometers sites. =
One of=20
them is Ben Williams, a graduate student at Missouri University of =
Science and=20
Technology, where Gao teaches. He explains the reason the seismometers =
are set=20
in a grid. "Because rather than seeing what's going on under the ground =
at a=20
specific point, they can pool the resources from all of these =
seismometers and=20
that's what's able to give them more of a visual picture of what's going =
on.=20
Rather than having just one point and seeing what's going on there, you =
have 20=20
points per state seeing what's going on at all times."
Senior =
geology=20
major Alicia Metzger from Missouri State University adds that the =
sensitive=20
instruments measure any sort of vibration. "They also perform what they =
describe=20
as a CAT scan, so that way we get an idea of what the mantle and =
underneath the=20
ground here =E2=80=94 the bedrock =E2=80=94 looks like. The whole =
project together collectively=20
will be able to give us a picture of what's going on in the North =
American=20
plate."
Keeping landowners in the loop
Today, the =
two=20
students are double-checking one of their candidate sites to make sure =
it's=20
still suitable. Kirby Farms is a scenic cattle ranch off the beaten =
path, with=20
rolling hills and bright green meadows.
Owner James Kirby jokes =
that=20
he's allowing EarthScope to set up a station on his property because =
they=20
offered him a large amount of money, then adds, seriously, "No, they =
just came=20
out and told me what they were going to do and wanted to know if we'd go =
along=20
with it. Why not? We have a fault line, the New Madrid, on the eastern =
side of=20
Missouri. If they gain some information, it will be =
something."
Metzger=20
says they like to keep the land owners involved in what they're doing. =
"We'll=20
send them newsletters regionally for their areas quarterly, that way =
they get an=20
idea of what's going on in their areas what's involved with their =
seismometers."=20
Kirby hauls out the all terrain vehicles, and the students make =
the=20
bumpy ride out to the site where they take some readings. They determine =
that it=20
is a good location for a monitor.
Workers will soon build a small =
underground station at Kirby Farms by digging a deep hole and =
reinforcing it=20
with concrete. Then a network of sensitive equipment, wires, and meters =
will be=20
installed to monitor the earth's activities. Through the use of cellular =
telephone and satellite signals, the station will transmit data for the =
next two=20
years.
Data to advance many scientific fields
While =
the=20
14-year project, funded by the National Science Foundation, may seem lengthy in =
human terms,=20
Gao says it's miniscule in geologic terms. But he says one of the =
important=20
things about this study, is that scientists don't have to wait until =
it's=20
finished to begin analyzing the data. EarthScope makes it available to =
everyone=20
via the internet through live streaming.
"People are already =
starting to=20
publish things," Stephen Gao reports. "So we are actually doing several =
things=20
at this date. We are trying to map the structure of eastern Nevada, for =
example.=20
We are trying to see why there are some very strange structures in New =
Mexico=20
and Colorado. There are papers already being published and on the way. =
You don't=20
have to wait for the end."
As researchers learn more, the =
information=20
will be used to help educate the public about earthquake science and =
safety. And=20
scientists and engineers hope to use what they learn from EarthScope to =
design=20
stronger earthquake-resistant structures, and improve earthquake and =
volcano=20
predictions.
From archaeology to zoology, from atoms to galaxies, Our World gives = a=20 state-of-the-art mix of news and features
Mor= e =C2=BB=20Watch: The United States debates cutting its carbon dioxide=20 emissions.
More = =C2=BB=20