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By:
Maribeth
Age: 13
Grade: 8
Michigan |
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WHEN I WAS IN THE FIRST GRADE A MAN LIVING IN CALIFORNIA PREDICTED THAT THERE WOULD BE AN EARTHQUAKE ALONG
THE NEW MADRID FAULT LINE AND THAT THIS EARTHQUAKE WOULD BE MAJOR
AND COULD OCCUR AT ANY TIME IN THE NEAR FUTURE. Many people living
in my town remembered or had heard stories from their relatives
about the three earthquakes that hit the Mississippi Valley in
the winter of 1811-1812. The fear of the accuracy of the prediction
and the possible consequences of such an earthquake led our school
district to initiate a program of earthquake awareness. Special
bells at school were sounded as a signal for students to drop
under the tables and desks as fast as possible. We practiced getting
off of buses and standing in doorways. We also took home information
sheets with facts on how to prepare for an earthquake at home
and the supplies needed for survival should a disaster occur.
Of course, the earthquake did not happen, and the man from California
died in obscurity. But it fostered within me a fascination and
fear of earthquakes that I still have to this day.
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History of Earthquakes
An earthquake is the sudden shaking, or shock movement, of Earth's
surface caused by the extreme release of energy deep within Earth's
crust. Almost all movement occurs along pre-existing breaks in
Earth. There are numerous faults that occur on Earth's surface,
and most of them remain quiet, while other faults are in a continuous
state of movement and account for the more than 100,000 recorded
quakes that occur during a year. According to the theory of plate
tectonics, Earth's crust is made up of several rigid plates that
are in continuous motion every day. Movement along already established
breaks in Earth's crust, otherwise known as geologic faults, causes
earthquakes. It is known that the underlying forces that cause
movement along the faults do not operate in the same violent and
convulsive fashion as the earthquakes themselves. These underlying
forces are always moving and bending the sheets of rocks that
lie on each side of the fault, storing up energy. Suddenly, the
force causes the rock along the fault line to break, move, and
the two parts to slip by each other.
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Earth movements, created by earthquakes, create four kinds of
waves. The L waves are long waves with a low frequency that move
along the surface of Earth's crust. These are the waves that cause
the most destruction to human lives and property. The R waves
also move along the surface and travel in a vertical plane in
the direction of the transmission. Both P and S waves travel through
the Earth. Compression waves, or P-waves, travel through both
solids and liquids. The P waves oscillate to and fro in the direction
of transmission, and the S waves move at right angles to the transmission.
Shear waves, or S waves, travel only through solids. After an
earthquake, the shock waves can be detected on the opposite side
of the globe, the compression waves arriving in about 22 minutes.
P and S waves travel away from the quake in large circles that
gradually get bigger as they pass through the Earth. All four
types of waves are strongest the closer they are to the center
of the earthquake.
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The study of the waves and the velocity of their travel is called
seismology and helps scientists to discover the type and density
of rock to be found in certain areas and in certain levels of
Earth. The crust, mantle, and core are easier to define and label
in any one certain area after the waves are recorded and studied.
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From Earthscope, p.15, Chris Pellar |
New Madrid Fault Line
On December 16, 1811, the greatest recorded earthquake to hit
the continental United States occurred in a small town called
New Madrid, Missouri, along the banks of the Mississippi River.
New Madrid, with a population of less than a thousand people,
was totally destroyed. The ground moved like waves in the ocean,
and dust filtered through the air and darkened the sky. Trees
tilted into each other, linked branches, and were then torn apart
when the trunks settled back into the soil. Great cracks opened
in the soil, and huge waves in the river capsized and sank many
boats and barges. Sandbars and entire islands disappeared, and
the topsoil of many farms totally disappeared underground. The
Great New Madrid Earthquake of 1811-1812, as this period of history
is now called, happened over a three month period with three main
shocks or earthquakes. According to historic records, the shocks
were estimated to be more than a magnitude 8.0, or maximum intensity.
When the first aftershocks had died down, another shock struck
on January 23, 1812. After two more weeks of relative quiet, the
last shock was felt on February 7, 1812. The Mississippi River
changed course and, some said, flowed backward for days. Two large
lakes, including Reelfoot in Tennessee, were formed in dropped
basins. The entire fault zone is believed to have ripped apart
in this series of earthquakes, and aftershocks were felt in the
immediate vicinity over a year later.
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The shocks were felt from Chicago and Detroit to Washington, D.C.,
and Boston. The entire eastern part of the country suffered with
aftershocks for as long as two years after the initial quakes.
Because this took place in the nineteenth century, transportation
and communication were extremely primitive. It took days for the
news of these earthquakes and their severity to reach all parts
of the United States. The United States was too young and poor
to attempt any in-depth study. Amateur scientists visited the
site, but the sparseness of the population and the looming War
of 1812 caused the entire nation to quickly turn its attention
to more pressing problems. The damage that could have occurred
if this area had been more populated was averted by the newness
of the country.
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This system is a series of faults beneath the continental crust
in a weak spot known as the Reelfoot Rift. Of course it cannot
be seen from the surface of the Earth. The fault extends 150 miles
southward from Cairo, Illinois, to Dyersburg, Tennessee. The past
20 years have shown scientists that the New Madrid fault affects
a much larger area than the California zone. The differences in
geology between the land east and west of the Rockies are significant
and indicate the need for quick action should an earthquake occur.
The loss of life and destruction of buildings only prove how much
more careful we need to be about where we live and how we live.
So why exactly do we still go back to rebuild after such great
destruction, which could happen again in the same place?
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The Present
Today, the Mississippi Valley is home to millions of people, including
those in the cities of St. Louis, Missouri, and Memphis, Tennessee.
This adds to the danger of destruction because most structures
are not built to withstand the severe shaking of an earthquake.
The Mississippi River attracts people because it is the lifeline
of commerce connecting the northern part of the United States
to the Gulf Coast. It is also the intersection of major highways
that connect the East Coast to the West Coast. The rich farmland,
beautiful wooded areas, and mountainous tourist attractions have
also encouraged people to settle in these areas or spend their
vacations here.
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Recent research indicates that most major earthquakes occur every
600 years. Unfortunately, the chance of a major earthquake hitting
the New Madrid fault line rises 7 percent for every 50 years that
passes. And of course, nature does not always follow the rule
of averages. Tremors are recorded daily in the Memphis and St.
Louis area and elsewhere in the Mississippi Valley frequently.
Earthquakes can strike suddenly and with no warning, and because
the most devastating earthquake in this nation's history occurred
along the New Madrid fault line, a sense of false security could
be the worst thing the people in this area could assume. The next
great earthquake will tax the economy and resources of the Central
Mississippi Valley region. And because this area has a substantial
amount of the nation's manufacturing facilities and one-third
of the nation's population, a major earthquake could place the
nation at risk. As power is lost, services disappear, and the
population has to learn to survive on their wits and what the
land can provide.
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From Hays |
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The development of long- and short-term prediction of earthquakes
is moving forward with the increase in scientific study, the ability
to study past earthquake cycles, the use of models, and better
instrumentation. The ability to assess construction costs as opposed
to the potential for the saving of lives has become a scientific
process. Unfortunately, most of the buildings in the New Madrid
fault line were not built to withstand the shaking caused by earthquakes.
The modern city of Memphis has been built along a bluff on the
Mississippi River. The Autozone corporate headquarters located
in Memphis is the first building to be built to possibly survive
the waves of an earthquake. Many organizations have banded together
with state and national government to implement plans of action
for the reduction in the loss of life and property damage along
this fault. These include the following:
1. The formation of the Central United States Earthquake Consortium
(CUSEC)
2. A plan for intensified study of the New Madrid Fault Zone
3. Earthquake education in the school curriculum
4. The observance of Earthquake Awareness Week
5. Volunteer earthquake advisory boards
6. Mapping earthquake hazards
and regional soil maps
7. Adopting building codes
8. Strengthening critical structures such as bridges, dams, etc
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From Berlin |
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No matter how many scientific instruments are created to predict
the possibility of a future disaster, you cannot prevent earthquakes.
An extensive program to reduce the vulnerability of society to
destructive earthquakes must be created with the ability to forecast
if an area is prone to disaster and what precautions should be
taken. Plans and people must be in place for quick aid and recovery
to an area that is struck by an earthquake. This includes the
alteration of existing structures to improve their performance
in the event of an earthquake. Even if structures could withstand
the ground shaking, there is the added hazard of foundation failure
causing buildings to topple over due to the ground giving way
underneath them. When nature or man-made disasters destroy cities,
they are almost always rebuilt, for the exact same reason, in
the exact same place. Most often cities are built in areas for
their climate, economic importance, strategic defense, and recreational
facilities. However, not taking all of the danger factors into
consideration before planning a city or town increases the hazards
of fire and flooding, which are very likely in earthquake-prone
cities. |
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References
Erickson, Jon. Volcanoes and Earthquakes. Tab Books Inc. Blue
Ridge Summit, Pennsylvania, 1998.
Lanham, Urless Norton. The Sapphire Planet. New York: Columbia
University Press, 1978.
Lee, Chris Eckstrom. Our Awesome Earth. Washington: Special Publications
Division, National Geographic Society, 1994.
Pellant, Chris. Earthscope. London: Tiger Books International,
1985.
World Book Encyclopedia. Volume 6. World Book Inc. 1990, USA.
Pg. 33
Penick, Jr., James Lal. The New Madrid Earthquake. Columbia, Missouri:
University of Missouri Press, 1981.
USGS. "Information on Earthquakes." 23 June 1998
http://easternweb.er.usgs.gov/eastern/earthquakes/ faq5a.html
http://www.ceri.memphis.ed.www/public info/faultfacts.html
http://www.ceri.memphis.ed.www/public info/follies.html
http://www.ceri.memphis.edu/www/research/shallow seimic.html
http://www.elwe.cer.memphis.edu/~seisadm/dgi-bin/eq_ceri.cgi:
http://www.quake.wr.usgs.gov/QUAKES/FactSheets/NewMadrid |
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