The New Madrid earthquake zone, located along the Mississippi River near Memphis, Tennessee, has received little attention in recent years. But in 1811 it was the site of the most powerful series of earthquakes ever known on earth. Some two million square miles were affected, and shocks were felt as far away as Montreal, Canada - 1,200 miles from the epicenter.
According to experts, another major earthquake will likely occur in the New Madrid Earthquake Zone in the next 50 years. With the aid of computer graphics, the geologic characteristics of the region and the tectonic nature of earthquakes are explained. Additionally, the relatively stable region of the central United States is compared to the well-known seismicity of California. This is a fascinating science adventure that, for many people, will hit very close to home.
'Interesting, easy to follow, full of good information, and well illustrated with high-quality computer graphics and live-action footage...effective in any historical geology or tectonics class to show how the understanding of ancient tectonic history can elucidate issues that face modern society.' ***** Journal of Geological Education
'Smoothly edited into a vibrant, coherent, accessible whole with an excellent balance of interviews to visuals. Highly recommended for classroom use in earth science courses and for the general public.' **** Video Rating Guide
'Explains the geologic origins of earthquakes, cites the difficulties of predicting action along the New Madrid Fault, and calmly alerts viewers to a hidden threat.' Booklist
Prose, Doug V. (screenwriter)
Prose, Doug V. (film producer)
Wescott, Don (narrator)
Edited by Laurie Schmidt; cinematography, Doug Prose; original music by Doug Prose, Mel Von Kriegenbergh, Ed Goldfarb; scientific advisor, Dr. Kaye Shedlock.
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Memphis, Tennessee. On the far
side of the Mississippi River,
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the land smooth\'s out in a broad level
plane. Below this veneer of rich farmland,
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one of the planet\'s most powerful
earthquake zones lies hidden.
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In recent history, the Earth is trembled
off from here but really enough to cause
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serious damage. So there hasn\'t
been much concern for earthquakes.
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The population has grown to over 10 million people
in the region, and most development took place
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with no regard for earthquake safety.
The earthquake zone lies buried
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in the heart of America. It trends along the
Mississippi River between Marked tree, Arkansas
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and Cairo, Illinois. Scientists call
it the New Madrid Seismic Zone,
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named after a small town in Southern Missouri.
This is not the original town we see here.
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The first one vanished in 1812 when
the strongest series of earthquakes
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ever known on earth tore the region apart.
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That was a longtime ago, but scientific evidence
shows that the New Madrid earthquake zone
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is still very much alive.
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On a clear winter night, the sky above the earthquake
zone lit up with what looked like lightning.
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Below, a massive temblor with a magnitude
of eight or higher struck near Marked Tree.
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A month later, another jolt as strong
as the first struck near New Madrid.
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Incredibly, a third great
quake, the strongest yet,
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rocked the area just 15 days later. Between
these shocks and for months afterward,
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the earth trembled constantly. \"Earthquakes
were so frequent\", an observer wrote,
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\"The earth was in continual agitation,
visibly waving as a gentle sea.\"
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The Mississippi River was profoundly
disrupted by the earthquakes.
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There are stories in the 1811 earthquake that the
very calm Mississippi River suddenly had rapids
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in several areas along it. If a
(inaudible) crossing the river moves,
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if it throws up part of the river floor, you will have rapids, you
will… And there were also stories that the river ran backwards
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in a few points. The eyewitness
accounts from 1811 and 12
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indicate that the river was essentially
unnavigable. There were vast amounts of
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down trees and debris floating in
the river, the banks had caved,
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sandbars that used to be in one location, perhaps, sunk and others
rose in other areas so that the entire character of the river
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was fundamentally different.
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The quakes caused large tracks of land to
warp upward while other tracks sank down.
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Reelfoot Lake near New Madrid was created when
the land heaved up and dammed a running creek.
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When it was all over, an
area the size of Tennessee
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bore the effects of the earthquakes, buildings
were damaged over an area as vast as
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the state of Texas.
Eyewitness accounts span
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the entire nation east of the
Mississippi River. St. Louis, Missouri,
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125 miles from New Madrid reported severe
shaking, badly cracked stone building,
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and hundreds of chimneys thrown down.
Similar reports came
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from the more distant city of
Cincinnati, Ohio, 300 miles away.
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The quake seismic waves traveled right through
the Appalachian Mountains to the East.
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They arrived forcefully on the Atlantic
Coast, 600 miles from New Madrid.
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In Charleston, South Carolina, cracks
opened in the mortar of stone buildings.
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The bells of St. Philip\'s Church rang out
for a short time. Clock stopped working
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in the coastal city of Savannah, Georgia
where four large shocks were felt.
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Furniture was tossed about in people\'s
homes. Further yet from New Madrid,
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moving furniture woke residents of Washington
DC who thought they were being robbed.
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Shaking interrupted an early morning meeting
of Congress. The earthquakes were felt sharply
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as far south as New Orleans. The local
newspapers reported little damage in the city.
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There was even a report of shaking
from the state of Florida.
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To the North, at least, eight shocks were distinctly
felt in Montreal, Canada, 1200 miles away.
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All in all, 2 million square miles,
well over a half the United States
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was shaken by the New Madrid earthquakes.
This is the largest area
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ever known to be affected by any
earthquake anywhere on earth.
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The great San Francisco earthquake in 1906 matched
the power of the strongest New Madrid shock.
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It had a Richter magnitude of 8.3,
enough to devastate San Francisco.
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Beyond the city, the quake had a
damage area of 12,000 square miles.
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That\'s 20 times smaller than the area of
damage for the New Madrid earthquakes.
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Earthquakes are normally seen
as a California concern.
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And while quakes are not as common
in the New Madrid earthquake zone,
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their enormous damage areas put millions of
people at risk in the Central United States.
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Damage areas are so large
partly because of the zones
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relation to global plate tectonics.
The zone lies at the core of
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the North American tectonic plate, one of 12 major
plates that form the outer skin of our planet.
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The plates are floating on molten material
below forcing them to crash together
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or pull apart at the edges. Over
90% of all earthquakes occur
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where plates meet. But the plate\'s cores
or cratons have remained relatively stable
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for billions of years. They have
become rigid. When earthquake strike,
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seismic waves travel great distances
through this dense solid rock.
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At the edge of many crustal
plates, the landscape reflects
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the violence of rocks grinding together.
California straddles the boundary
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between the North American and Pacific plates.
The rugged landscape is geologically very young
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and seismic waves break up quickly in
the broken landscape they created.
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But there are exceptions.
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October 17th, 1909,
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San Francisco\'s Marina District was heavily
damaged by the Loma Prieta earthquake,
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but the quake\'s epicenter was over 60 miles
away. In between the heavily populated bay area
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suffered relatively little damage.
The Marina District was hard hit
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because it is built on
very soft sand and mud,
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ironically part of it was once a lagoon, which was
filled in with sand and rubble from the 1906 earthquake.
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Seismic waves spread away from the Loma Prieta
quake\'s epicenter through hard bedrock below.
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But nearing the Marina, they slowed
down in the loose surface materials.
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This caused the waves to grow into
destructive surges at ground level.
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The New Madrid earthquake zone
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lies buried in the Mississippi River valley.
Connecting with the river is a vast network of
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more rivers, streams, and lakes, all draining
the wet climate of the mid-continent.
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These waterways eroded the land and
left valleys of loose sediment
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over hard crustal rocks below,
a dangerous combination.
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Seismic waves travel great distances through the rigid crust
then build to violent force in soft river valleys sediments.
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By coincidence, this is
where most people live.
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The face of the New Madrid earthquake
zone has changed dramatically
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since the great quakes of 1811 and 12.
The region has become
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a major agricultural and industrial producer. The
busiest transportation corridor in the nation,
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the Mississippi River, winds its way
through. Crowded interstate highways
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and the dense web of railroads
crisscross the earthquake zone.
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Belowground, natural gas and oil pipelines connect
refineries in the South with customers in the Northeast
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where one quarter of the
nation\'s energy is consumed.
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In Memphis, Elvis Presley\'s Graceland attracts
more visitors than any other home in America,
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except the White House. And Memphis airport serves as distribution
headquarters for the world\'s biggest freight carrier.
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The wilderness of 1811 and 12
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is indeed gone. And as the
works of people replaced it,
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the New Madrid earthquake zone remains
silent. So the area grew up unarmed
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against the fury of earthquakes. When an
earthquake does happen in Central Eastern US,
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the damage areas are gonna be a
lot bigger and it\'s gonna be
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a higher density of damage then you would see
for similar sized earthquake in California.
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Most of the buildings in the
Central Eastern United States
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are constructed from unreinforced masonry
which has virtually no resistance
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to strong ground shaking. In
fact, the last major earthquake
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that happened in Central
Eastern US was in 1895,
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when we developed this whole new infrastructure.
Since then, it hasn\'t been tested
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by a strong damaging earthquake. The same
way that California seems to get tested
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every 10 or 20 years, there\'s a strong
earthquake that knocks down buildings,
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they put up new ones, they\'re designed to
withstand, resist those forces better.
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But we haven\'t had the benefit of that
kind of testing in the Central Eastern US.
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So when one finally does happen, the
other projections and damage is gonna be
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a lot more serious. Suzanne, can you
come look at this, please? Sure. Yeah.
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When will the next large earthquake strike?
What will it do to the Central United States?
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For decades, scientists have
been searching for the answers,
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but the earthquake zone does not reveal its secrets
easily. The Mississippi River running chocolate brown
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with silt buried the zone
under 3,000 feet of mud.
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Advanced earthquake studies developed in California
do not work well here. We have to sample everything
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from the surface because the seismicity
is between 5 and 15 kilometers deep.
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You can\'t dig a hole that deep and look for something. We don\'t
quite have that technology. And in San Andreas like situation,
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you can see the fault. You can walk out and
you can find the trace of it, you can see it
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in the dramatic topography that creates
San Andreas Lake. But in New Madrid,
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it\'s not right there for us to say.
It\'s not right there for us to map.
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Borrowing methods used for oil exploration,
scientists looked through the surface layer of mud
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and probed the rocks below. In the
early 19070s, they discovered
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a buried swath of fractured twisted rocks
about 200 miles long and 40 miles wide.
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The structure was named the Reelfoot Rift.
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The late Dr. (inaudible), a geophysicist at
St. Louis University, used newspaper reports
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to locate earthquakes in the rift. His
results have stood the test of time
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despite the reliability of old news stories. Modern
instruments corrected the reliability problem.
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Up until 1974,
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we just knew that earthquakes were
occurring down in the Bootheel, Missouri.
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1974, St. Louis University was
able to establish a modern, dense,
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regional size and graphic network.
As soon as that was installed
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and earthquakes were recorded,
very strong patterns emerged
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uh… showing where the earthquakes
occurred in the region.
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We with our seismic networks can record
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umm… and locate an earthquake about every two
days, and there will be an earthquake about
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92 (inaudible) to 2.5. And certainly
that level of activity, number magnitude
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five earthquakes that we have seen in the last
30 years is much larger than anywhere else
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in the Eastern United States.
So relative to, you know,
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other areas of the Eastern United
States, New Madrid is a hotspot.
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The earthquakes trace out a zigzag pattern when plotted
on a map, but their epicenters are actually located
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2 to 10 miles below the surface, along
deep faults in the earth\'s crust.
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These cubes represent earthquakes
along deeply buried faults,
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swinging below New Madrid, seismicity
picks up then dies out farther north.
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To learn what causes these quakes, we must
journey back in time half a billion years.
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At that time, the continent began to
slowly pull apart. Molten magma swelled up
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from below causing the crust to bulge
and crack open up the surface.
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Extreme heat and pressure continued splitting
the rigid crust allowing magma to shoot up
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through fissures and erupt on the surface
forming volcanoes. The Reelfoot Rift
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was tearing the continent in half.
Now this is a fairly common
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umm… geologic process worldwide.
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And when it happens on a large global
scale, it can form new oceans,
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new ocean is opening up right now
in the Red Sea area for instance.
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So but many rifts are not successful,
they fail, they never make it
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to the stage of actual splitting a
continent and creating new oceanic crust.
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And Reelfoot rift was
one of the (inaudible).
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Over the next 300 million years, the
volcanoes and the doomed rift went extinct.
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The thin fractured crust cooled back down collapsing
under its own weight to form a long wide valley.
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Ancient oceans then flooded much of
North America from millions of years.
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They left behind thousands of feet of sediment
which collected in the sunken Reelfoot rift.
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Through the eons, the rift made several
weak attempts to pull apart again.
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Magma started up old fractures
but never reached the surface.
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Sixty million years ago, rifting stopped.
The crust sank down once again.
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And natural erosion filled the rift
with another layer of sediments.
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The Mississippi River began flowing down the rift
valley after the last ice age about 10,000 years ago.
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But down below, the shattered
rifted rocks remained.
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We\'ve got a much weaker overall crust
than you would out in the crater.
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And that\'s where we find larger quarts
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and the stable continental areas.
So we feel that
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umm… as the… as the ancient faults
of the Reelfoot rift system,
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they\'re regenerating earthquakes today.
The ancient faults are kept alive
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by subtle tectonic forces. Stress in the
earth\'s crust is squeezing the rift
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from the east and west. When stress is great enough,
the old faults which are at an angle to the pressure,
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slips suddenly causing earthquakes.
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The southern end of Reelfoot rift near
Memphis is currently under the most stress.
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With a tendency for big earthquakes to strike
at the ends of faults, this is a good candidate
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for the zones next big quake.
The question is when.
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I would not be surprised to witness a greater than
magnitude six earthquake in my lifetime out here.
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I\'m comfortable that we know roughly
00:16:55.000 --> 00:16:59.999
where in the broad sense, somewhere in
the current very active seismic zones,
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there will be a magnitude six or greater
earthquake certainly in my lifetime,
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but we still have a lot more to learn. We don\'t
know when the magnitude eights will occur,
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probably not in my lifetime but possibly.
We just don\'t know.
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With few defenses against earthquakes,
even a magnitude six to seven earthquake
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could inflict heavy losses in this region.
Damage will be concentrated
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where geologic conditions are most hazardous.
A fascinating phenomenon called liquefaction
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will be widespread along rivers
and streams. It\'s a phenomenon
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where earthquake waves start
shaking the sand. Soft wet sand
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will start compacting together, like when
you take a box of corn flakes and shake it
00:18:10.000 --> 00:18:14.999
and the corn flakes in the box settle. That happens
with the sand. And as the sand starts to settle,
00:18:15.000 --> 00:18:19.999
the water that\'s between the grains of sand
tries to get out from between the grains.
00:18:20.000 --> 00:18:24.999
And if there\'s something solid on top of the
stand like a layer of clay, the pressure breaks
00:18:25.000 --> 00:18:29.999
the surface layer of clay and sand
will come erupting onto the surface
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in sort of a liquefied form, so we call it
liquefaction. And what this often causes is,
00:18:35.000 --> 00:18:39.999
first of all, the ground to break up.
The ground also loses
00:18:40.000 --> 00:18:44.999
all capacity to hold up objects such as
building, so buildings will settle, sink,
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or tilt during liquefaction. And many
earthquakes, there are things called
00:18:50.000 --> 00:18:54.999
sand blows which form. The upper layer of clay will
crack and the sand will come erupting to the surface
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in sort of a volcano and form a
circular patch of sand maybe 20-40 feet
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across of the crater in the middle. That\'s very
typical. We see it in almost any earthquake
00:19:05.000 --> 00:19:09.999
over magnitude six anywhere in the world.
What I\'m going to do is
00:19:10.000 --> 00:19:14.999
walk on this pristine sand
that can bear my weight.
00:19:15.000 --> 00:19:19.999
And once I start bouncing up and down, you\'ll
see that as the sand starts to compact
00:19:20.000 --> 00:19:24.999
and the water comes out of its pores,
the sand liquefies losing all ability
00:19:25.000 --> 00:19:29.999
to bare my weight. And if we watch
afterwards, we will see that
00:19:30.000 --> 00:19:34.999
water erupting in the surface
in miniature sand boils.
00:19:35.000 --> 00:19:39.999
This is a small sand filled
fissure caused by liquefaction
00:19:40.000 --> 00:19:44.999
during the 1811 and 12 earthquakes. From the air,
huge light-colored patches of liquefied sand
00:19:45.000 --> 00:19:49.999
from those quakes are plainly
visible in farmers\' fields today.
00:19:50.000 --> 00:19:54.999
Liquefaction during the 1811 and 12 quakes
devastated a 1,400-square-mile area
00:19:55.000 --> 00:19:59.999
along the Mississippi River.
Today, this same area
00:20:00.000 --> 00:20:04.999
is covered with thousands of farms and
many communities. Highway 55 traverses
00:20:05.000 --> 00:20:09.999
the entire liquefaction zone. A modern
well build interstate, it is defenseless
00:20:10.000 --> 00:20:14.999
against a liquid-like foundation. The earth
levees along the river are also vulnerable,
00:20:15.000 --> 00:20:19.999
especially during high flood stage.
The river\'s natural banks
00:20:20.000 --> 00:20:24.999
now lined with petroleum storage tanks,
grain-loading facilities, original power plant,
00:20:25.000 --> 00:20:29.999
and long-bridge approaches are especially
vulnerable. Failure of these kind of riverbanks
00:20:30.000 --> 00:20:34.999
normally occurs by a process
that we call lateral spreading
00:20:35.000 --> 00:20:39.999
which occurs when liquefied sand and water
layers beneath the surface of the ground
00:20:40.000 --> 00:20:44.999
are shaken repeatedly over a long period
of time during a major earthquake.
00:20:45.000 --> 00:20:49.999
But the eyewitness accounts from the 1811 and 12
earthquakes indicate that even those low riverbanks
00:20:50.000 --> 00:20:54.999
experienced massive failure.
Transportation may be disrupted for years
00:20:55.000 --> 00:20:59.999
by liquefaction alone, but other earthquake
effects will add to the problem.
00:21:00.000 --> 00:21:04.999
In a future, major earthquake,
there\'s very little doubt
00:21:05.000 --> 00:21:09.999
that there will be major landsliding from bluff such as this
as well as bluffs that are farther away from the river.
00:21:10.000 --> 00:21:14.999
Large amounts of this land will
simply flow towards the river
00:21:15.000 --> 00:21:19.999
and trees and farmland and the ground
itself will simply be precipitated
00:21:20.000 --> 00:21:24.999
into the river. When we think ahead to future
possible earthquakes in the midcontinent,
00:21:25.000 --> 00:21:29.999
navigation is probably one of the issues
that we ought to deal with most seriously
00:21:30.000 --> 00:21:34.999
because obviously, a large
amount of barge traffic
00:21:35.000 --> 00:21:39.999
goes up and down the Mississippi River, and after a major
earthquake, it is likely that the river would be unnavigable
00:21:40.000 --> 00:21:44.999
for quite some period of time,
maybe weeks or even months.
00:21:45.000 --> 00:21:49.999
00:21:50.000 --> 00:21:54.999
Landslides and liquefaction are triggered
by strong shaking during earthquakes.
00:21:55.000 --> 00:21:59.999
By itself, shaking is a serious threat to weak
structures. Most vulnerable are old bridges
00:22:00.000 --> 00:22:04.999
and unreinforced masonry
buildings built on lose ground.
00:22:05.000 --> 00:22:09.999
Unfortunately, many historic ornate buildings around the
New Madrid earthquake zone fall under this category.
00:22:10.000 --> 00:22:14.999
When most of us think of earthquakes,
00:22:15.000 --> 00:22:19.999
we pictured gaping fissures like this one.
This is indeed a common scene
00:22:20.000 --> 00:22:24.999
when a quake strikes California. The
Landers quake in 1992 opened fissure
00:22:25.000 --> 00:22:29.999
50 miles long across the floor of the Mojave Desert.
But the faults of the New Madrid quick zone
00:22:30.000 --> 00:22:34.999
are too deeply buried to rupture the
ground except in massive quakes.
00:22:35.000 --> 00:22:39.999
Liquefaction, shaking, and landslides are the
main effects of earthquakes in this region.
00:22:40.000 --> 00:22:44.999
And the city most threatened by earthquakes is
the Blues music capital of the world Memphis.
00:22:45.000 --> 00:22:53.000
00:22:55.000 --> 00:22:59.999
As musicians play on Beale Street,
scientists from Memphis State University
00:23:00.000 --> 00:23:04.999
are evaluating Shelby County\'s public
buildings and bridges for earthquake safety.
00:23:05.000 --> 00:23:09.999
Preliminary results are sobering. One out of four
hospitals are in the highest seismic risk category,
00:23:10.000 --> 00:23:14.999
25% of the public schools,
and 15% of the fire stations
00:23:15.000 --> 00:23:19.999
also fall in this category. A
sampling of the county\'s 900 bridges
00:23:20.000 --> 00:23:24.999
showed that one out of four are
at the highest level of risk.
00:23:25.000 --> 00:23:29.999
Seismic evaluation of public utilities and
other critical lifelines is also underway.
00:23:30.000 --> 00:23:34.999
These studies will guide the strengthening of
only the most dangerous and critical structures.
00:23:35.000 --> 00:23:39.999
Retrofitting is expensive and there are
a great number of weak facilities.
00:23:40.000 --> 00:23:44.999
On the other hand, building new buildings to
be earthquake safe raises construction costs
00:23:45.000 --> 00:23:49.999
only 10% on average. But earthquake
codes are weak to non-existent
00:23:50.000 --> 00:23:54.999
in the New Madrid quake zone. The
state of Kentucky is an exception.
00:23:55.000 --> 00:23:59.999
They adopted modern earthquake codes in
1981. And recently, surrounding states
00:24:00.000 --> 00:24:04.999
are taking earthquakes more seriously. Researchers
found new evidence of one or more massive quakes
00:24:05.000 --> 00:24:09.999
near Vincennes, Indiana. The large
cities of Indianapolis and Evansville
00:24:10.000 --> 00:24:14.999
are less than 100 miles away. Chicago, Illinois
built on a veneer of very loose lake muds
00:24:15.000 --> 00:24:19.999
is 200 miles away. Skyscrapers
are in danger of excessive swing
00:24:20.000 --> 00:24:24.999
high-amplitude seismic waves.
00:24:25.000 --> 00:24:33.000
00:24:40.000 --> 00:24:44.999
There\'s another way to view this scenario. Earthquakes
are at the very root of this region\'s prosperity.
00:24:45.000 --> 00:24:49.999
The Mississippi River flows through here
because rifting opened a natural pathway
00:24:50.000 --> 00:24:54.999
to the sea. Earthquakes
literally shaped this rich land
00:24:55.000 --> 00:25:00.000
and will continue to do so.