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Scientists have pinpointed a set of faults in the Midwest
that cause severe earthquakes every 500 years. The
quakes are so powerful that they can cause the
Mississippi River to temporarily flow backwards.
Arkansas Quakes Could Offer Warning
By JON GAMBRELL,
AP
posted: 11-28-08
filed under: National News, Natural Disasters News, Science
News
LITTLE ROCK, Ark. (Nov. 28, 2008) - A series of small
earthquakes that rattled central Arkansas in recent weeks could be
a sign of something much bigger to come.
By this weekend, seismologists hope to install three measurement
devices to gather data about future temblors in the area. That
information could show whether the rumbles come from heat-related
geological changes or from an undiscovered fault — which could
mean a risk of substantial earthquakes in the future.
“The potential for generating a high-magnitude earthquake is
real," said Haydar Al-Shukri, director of the Arkansas Earthquake
Center at the University of Arkansas at Little Rock.
Five earthquakes ranging in magnitude from 2.2 to 2.7 have hit
central Arkansas this month. Quakes with a magnitude of 2.5 to 3
are typically the smallest felt by people.
While hundreds of earthquakes occur each year, including
several in Arkansas, the location of the recent ones give Al-Shukri
pause. Arkansas quakes generally occur in the state's northeast
corner, part of the New Madrid Seismic Zone, where three temblors
with magnitudes of around 8 struck during the winter of 1812 and
smaller ones continue today.
But central Arkansas does not have any seismic history, Al-Shukri
said.
"It is abnormal. It is significant," he said. "We need to
carefully watch this activity."
The area does not have any permanent seismograph, so
researchers asked the University of Memphis in Tennessee if they
could use its portable equipment. The nearest seismographs aren't
close enough to provide the detailed readings scientists need to
determine what could be causing the tremors or properly locate
their origin, said Scott Ausbrooks, the geohazard supervisor for
the Arkansas Geological Survey.
"I don't know if you've looked at a map of where these events
are located, but they've got a scatter on them," he said. "We're
thinking this is probably the inherited error built in when you
try to locate events of this small a magnitude from that far
away."
Ausbrooks said officials would install the three seismographs
around Magnet Cove, a Hot Spring County community near where a
magnitude-2.7 earthquake hit on Nov. 1. Residents told police
dispatchers they heard what sounded like an explosion.
One possible culprit could be a hydrothermal quake, caused by
extremely hot fluid pushing into rocks under the surface. The hot
fluid percolates into the cracks of the rocks and causes movement,
Al-Shukri said.
That theory matches the geologic history of the area. Central
Arkansas is home to Hot Springs, a city that grew up around its
namesake spas. The springs have 143-degree waters rushing to the
surface continuously.
If that's the case, the earthquakes likely wouldn't pose a
drastic danger to the area, Al-Shukri said. At their strongest,
such quakes reach only a magnitude of 5, the U.S. Geological
Survey's threshold for "moderate."
However, if the earthquakes are caused by a previously unknown
fault, that could mean a much more powerful temblor in the future.
A recently discovered fault in eastern Arkansas near Marianna
caused an earthquake with a magnitude of between 7.2 and 7.5 in
the past 5,000 years, Al-Shukri said. That could cause widespread,
heavy damage.
"Now, it's not active, but in geologist time, that's
yesterday," he said.
Ausbrooks wouldn't speculate on what could be causing the
earthquakes, saying he wanted to see what data the seismographs
capture. However, he acknowledged an unknown fault could be
running through the area.
"There are numerous faults across the state, both known and
unknown," Ausbrooks said. "This area has got a lot of faults
associated with it from the mountain building of the Ouachitas,
but they're considered inactive."
Copyright 2008 The Associated Press.
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NEW
MADRID
Mag. 2.0 April 23 07:21:26 36.270 -89.500 7.2 2
km (1 mi) WNW of Ridgely, TN
Mag. 1.7 April 23 17:05:49 35.530 -84.500 10.9 5
km (3 mi) ENE of Niota, TN
Mag. 1.8 April 23 22:54:59 36.520 -89.580 7.1 3 km
(2 mi) E of Marston, MO
Mag. 1.5 April 24 05:12:34 36.490 -89.550 8.4 6 km
(4 mi) ESE of Marston, MO
Mag. 2.5 April 25 00:45:46 35.910 -89.950 12.2 4
km (2 mi) SW of Blytheville, AR
Mag. 1.9 April 25 01:17:28 35.770 -90.150 0.4 9 km
(5 mi) W of Victoria, AR
Mag. 2.4 April 23 07:11:19 36.270 -89.500 7.1 2 km
(1 mi) WNW of Ridgely, TN
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USGS Downgrades Magnitude of Aftershock to
4.0
Created: 4/21/2008 1:28:14 AM
(KSDK) -- An aftershock originally believed
to be a 4.5 magnitude earthquake, has been
downgraded to a 4.0 quake.
The earthquake happened at 12:38 a.m. on Monday
about five miles from Mt. Carmel,
IllinoisA much weaker 2.2 aftershock
was recorded in the same area at 7:58 a.m.,
which was too weak to be felt in St. Louis.
There have been no reports of additional damage
or injuries.
The tremor follows a weekend filled with
aftershocks following a 5.2 earthquake that
occurred at 4:37 a.m. Friday.
The United States Geological
Survey reports 19 aftershocks between the
initial quake and including this morning's two
tremors.
Seismologists say aftershocks can last for a
week or more following an earthquake.
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Another Earthquake
Strikes Southern Illinois Along Wabash Valley Fault Line
April 21,
2008 5:45 a.m. EST
Linda Young - AHN Editor
Mount Carmel, IL (AHN) - A 4.5 magnitude
earthquake struck Southern Illinois early Monday
morning, the latest in a string of 18 earthquakes
in the region since a 5.2 magnitude quake struck
Friday morning, according to the U.S. Geological
Survey.
There were no immediate reports of damage. It
was the strongest quake since Friday. None of the
previous 16 aftershocks since the initial quake on
Friday was above 3.9 magnitude.
The quake struck at 12:38 a.m. CT about 131
miles east of St. Louis and 37 miles
north-northwest of Evansville, Indiana. It was
centered five miles northwest of Mount Carmel and
about 11 miles southeast of West Salem, according
to reports.
Friday's earthquake occurred in West Salem and
there were reports of minor damage.
The earthquake on Friday was the first in the
region in 40 years. The initial quake was felt as
far north as Chicago and west in St. Louis. These
earthquakes are on what is known as the Wabash
Valley fault.
"The largest historical earthquake in the
region -- magnitude 5.4 -- damaged southern
Illinois in 1968," the USGS told CNN news.
That 1968 quake, however, was on a different
fault line. It was on the New Madrid fault line
that extends north to Chicago and south to
Memphis. The 1811 and 1812 earthquakes on that
fault line were among the largest in the nation.
The 1811 quake rang church bells 1,000 miles away
in Boston, Massachusetts. The 1812 quake caused a
change in the course of the Mississippi River and
damage was reported as far away as Charleston,
South Carolina and Washington, D.C.
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A magnitude-5.2 earthquake, centered
131 miles east of St. Louis, Missouri,
shook southern Illinois early Friday,
according to the U.S. Geological Survey.
There were few reports of damage
immediately after the predawn quake, which
struck at 4:36 a.m. (5:36 a.m. ET), but
CNN affiliate WHAS-TV in Louisville,
Kentucky, showed footage of rubble left in
a street after a cornice fell off a brick
building there.
The epicenter of the earthquake was
about three miles below ground, six miles
northwest of Mount Carmel, Illinois, and
38 miles north-northwest of Evansville,
Indiana, according to the USGS
Copyright
2008 CNN. All rights reserved.
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This map from the U.S. Geological Survey Web site shows
the center of an earthquake that rocked the Midwest at 5:37
a.m. today.
http://earthquake.usgs.gov/eqcenter/recenteqsww/Maps/
10/270_40.php.
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http://earthquake.usgs.gov/eqcenter/recenteqsus/Maps/US10/32.42.-95.-85.php
Region: ILLINOIS
Geographic coordinates: 38.520N, 87.872W
Magnitude: 5.4 Mw
Depth: 5 km
Universal Time (UTC): 18 Apr 2008 09:36:56
Time near the Epicenter: 18 Apr 2008 03:36:56
Local standard time in your area: 18 Apr 2008 01:36:56
Location with respect to nearby
cities:
12 km (7 miles) E (90
degrees) of West Salem, IL
14 km (8 miles) NE (53 degrees) of Bone Gap, IL
14 km (9 miles) W (266 degrees) of Allendale, IL
67 km (41 miles) NNW (335 degrees) of Evansville, IN
206 km (128 miles) E (93 degrees) of St. Louis, MO
http://earthquake.usgs.gov/eqcenter/recenteqsus/Maps/US2/35.37.-89.-87.php
Earthquake rattles Illinois
4-18-08
Earthquake shakes central
Indiana, Illinois
West Salem, Ill.
A 5.4 magnitude earthquake that appeared to rival the
strongest recorded in the region rocked people up to 450
miles away early Friday, surprising residents unaccustomed
to such a powerful Midwest temblor.
The quake just before 4:37 a.m. was centered six miles
from West Salem, Ill., and 66 miles from Evansville, Ind. It
was felt in such distant cities as Chicago, Cincinnati,
Milwaukee, and Des Moines, Iowa, 450 miles northwest of the
epicenter, but there were no early reports of injuries or
significant damage.
“It shook our house where it woke me up,” said David Behm
of Philo, 10 miles south of Champaign. “Windows were
rattling, and you could hear it. The house was shaking
inches. For people in central Illinois, this is a big deal.
It’s not like California.”
Bonnie Lucas, a morning co-host at WHO-AM in Des Moines,
said she was sitting in her office when she felt her chair
move. She grabbed her desk, and then heard the ceiling
panels start to creak. The shaking lasted about 5 seconds,
she said.
The quake shook skyscrapers in Chicago’s Loop, 240 miles
north of the epicenter, and in downtown Indianapolis, about
160 miles northeast of it.
Irvetta McMurtry of Cincinnati said she felt the rattling
for up to 20 seconds.
“All of a sudden, I was awakened by this rumbling
shaking,” said McMurtry, 43. “My bed is an older wood frame
bed, so the bed started to creak and shake, and it was
almost like somebody was taking my mattress and moving it
back and forth.”
Lucas Griswold, a dispatcher in West Salem, said the
Edwards County sheriff’s department received reports of
minor damage and no injuries.
“Oh, yeah, I felt it. It was interesting,” Griswold said.
“A lot of shaking.”
Indiana State Police spokesman Sgt. Todd Ringle in
Evansville said there were no immediate reports of damage.
The quake occurred in the Illinois basin-Ozark dome
region that covers parts of Indiana, Kentucky, Illinois,
Missouri, and Arkansas and stretches from Indianapolis and
St. Louis to Memphis, according to the U.S. Geological
Survey.
The organization’s Web site said earthquakes occur
irregularly in the area, and that the largest historical
earthquake in the region — also a magnitude 5.4 — caused
damage in southern Illinois in 1968.
"Just hang tight and let us find out what is going on,
but get educated and learn what to do when there is an
earthquake," said Pam Bright, director of public information
and outreach for the Indiana Department of Homeland
Security.
She said that information is available at the
department's Web site at www.in.gov/dhs.
Earthquake felt in northern Indiana
 
Posted:
April 18, 2008 02:21 AM PST
FORT WAYNE, Ind. (WANE) - A moderate
earthquake shook many residents in their
beds this morning in northeastern
Indiana.
According to the United States Geological
Survey, Earthquake Information Center, the
earthquake occurred at 5:37 am Indiana
time this morning and was a magnitude 5.4.
The epicenter for this earthquake was 7
miles from west Salem Illinois and 61
miles north northwest of Evansville
Indiana.
The Associated Press reports that tall
buildings were swaying in Indianapolis.
According the USGS a quake of the same
magnitude was recorded with an epicenter
in west Salem, Illinois in 1968. The 1968
quake was felt across 23 states.
The most famous quake along the New Madrid
fault happened in New Madrid, MO in 1812
when it was reported that the Mississippi
flowed the opposite direction or
'backwards'.
Friday's earthquake comes on the
anniversary of the Great 1906 San
Francisco Earthquake that ranks as one of
the most significant of all time.
Links
with more information:
U.S. Geological Survey
World Data Center
United States Educational
Seismology Network
Wabash Valley Seismic Zone
The Great 1906 San Francisco
Earthquake
Yet Another EQ - 3
Miles From New Madrid
[link
to earthquake.usgs.gov]
2.5
Date-Time Sunday, January 20, 2008 at 09:13:54 UTC
Sunday, January 20, 2008 at 03:13:54 AM at epicenter
Location 36.630°N, 89.560°W
Depth 9.9 km (6.2 miles)
Region SOUTHEASTERN MISSOURI
Distances 5 km (3 miles) NNW (335°) from New Madrid,
MO
6 km (4 miles) ENE (59°) from North Lilbourn, MO
6 km (4 miles) NE (47°) from Lilbourn, MO
172 km (107 miles) NNE (12°) from Memphis, TN
230 km (143 miles) SSE (165°) from St. Louis, MO
Location Uncertainty horizontal +/- 0.3 km (0.2
miles); depth +/- 0.6 km (0.4 miles)
Parameters Nst= 35, Nph= 47, Dmin=4.4 km, Rmss=0.08
sec, Gp= 40°,
M-type=duration magnitude (Md), Version=A
Source Cooperative New Madrid Seismic Network
Event ID nmhwb0120a
The New Madrid fault
Located in the "Boot Heel" of Southeast Missouri, the town of New
Madrid sits on a major fault that extends into Arkansas. In the
early 1800's, a series of magnitude 8 earthquakes occured. Written
accounts from eyewitnesses to this earthquake are quite remarkable,
see more details below.
The size of this event leads geologists to suspect the the New
Madrid fault is a failed rift valley: a place where the North
American continent almost split into two pieces. What we know from
history is that if something geologic has happened in the past, it
can happen in the future. Earthquakes are not a matter of *if* they
will happen, but *when* they will happen
May 2, 2007) - Scientists have finally figured out
what might have caused a series of devastating
earthquakes that struck the Midwest nearly 200 years
ago at a set of faults that has confused geologists
for a long time.
And the results suggest the region, still seismically
active today, is going to keep shaking for a long
time, and another big one will hit on the same
500-year cycle that has rocked the Heartland for as
far back as records, legends and memory serve.
The largest of three or four big seismic events that
stretched from December 1811 to February 1812 is
called the New Madrid Earthquake and had an estimated
8.0 magnitude, strong enough to cause the nearby
Mississippi River to temporarily flow backward. Its
epicenter was in the town of New Madrid in southeast
Missouri, near the Kentucky and Tennessee state lines.
Hundreds of aftershocks followed for several years.
The damage from the New Madrid quake was bad enough in
the early 19th century—half of the town was destroyed,
but with many more people and buildings now in the
area, a similar event in the region today would be
devastating, seismologists and engineers agree.
More to Come
The seismic zone today generates about 200 tiny
quakes annually, but it also let loose a magnitude 4.1
quake in February 2005 and a magnitude 4.0 quake in
June 2005. The U.S. Geological Survey says there is a
9-in-10 chance of a magnitude 6 or 7 temblor occurring
in this area within the next 50 years.
These mid-continent temblors have long fascinated
seismologists because of the mysterious origin of
earthquakes that occur not at the edges but in the
center of tectonic plates such as the North American
Plate that underlies the continent.
One team of seismologists had thought that high
density pillow lavas in the lower crust beneath the
New Madrid region could have pulled the crust downward
and thereby generated surface stresses that triggered
the quakes.
Now, Allessandro Forte of the Université du Québec
à Montréal and his colleagues have arrived at a more
dramatic mechanism—an ancient, giant slab of Earth
called the Farallon slab that started its descent
under the West Coast 70 million years ago and now is
causing mayhem and deep mantle flow 360 miles beneath
the Mississippi Valley where it effectively pulls the
crust down an entire kilometer (.62 miles).
"This remarkable localization of flow in the mantle
below New Madrid, originating so deep below the
surface, was completely unrecognized prior to our
work," Forte told LiveScience.
Slabs like this that sink oceanic crust are called
subduction zones, and those adjacent to Japan produce
intense and damaging seismic activity.
"We have discovered an analogous subduction zone, deep
inside the Earth below the central Mississippi River
Valley," Forte said.
Forte and his colleagues at the University of Toronto
and the University of Texas based their findings on
high-resolution seismic tomography images that were
used to predict the topography and viscous flow of the
mantle under and around North America. They used the
model to focus on the New Madrid seismic zone and
propose that the descending slab and associated mantle
flow directly below the New Madrid seismic zone
strains the overlying crust, causing seismic ruptures.
The results were published in a recent issue of
Geophysical Research Letters.
The Farallon plate will continue to descend into
the deep mantle and thus to cause mantle downwelling
in the New Madrid region for a long time.
"[This] suggests that the seismic risk in the New
Madrid region will not fade with time," Forte said.
The fault structure under the New Madrid region is a
"failed rift" created by the opening of the ocean that
later became the Atlantic Ocean 650 to 600 million
years ago, Forte said.
That activity also caused rifts in the St. Lawrence,
Saguenay and Ottawa river valleys in Canada, where
there is similar mid-continental quaking, he said.
Another set of faults far from the boundaries of the
North American Plate are associated with the
Keweenawan Rift, a 1240-mile-long rift in the area
surrounding Lake Superior.
(c) 1999-2007 Imaginova Corp. ALL RIGHTS RESERVED.
2007-05-03
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3-18-02 - I had a waking vision that an earthquake was going to occur along the Mississippi River that was so
large, that it created an island to form all the way from St. Louis to the Minnesota border.
After that, I saw a man standing at a podium in Congress, named McMullen who was asking for resources. He did
this twice.
There are McMullens in several states, so this would be probable.
NOTE: Research does not show any likelihood that this could occur, but that would make it all the more devastating
if it did occur without warning.
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THE NEW MADRID FAULT ZONE
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Illinois, other states feel 3.9 earthquake
Items compiled from Tribune news services
Published June 21, 2005
CLINTON, KENTUCKY -- A small earthquake centered in western Kentucky
rattled residents across parts of Illinois, Kentucky and three other states
Monday morning. No damage was reported.
The 3.9 magnitude quake centered near Clinton hit at 7:21 a.m. and was felt
in southern Illinois, western Kentucky, southeast Missouri, northwest
Tennessee and eastern Arkansas, said Diane Noserale, spokeswoman for the
U.S. Geological Survey in Reston, Va.
It was the second quake to hit the area in a matter of hours along the
New Madrid Fault System, Noserale said. A 2.7 magnitude quake Sunday in the
same area was felt in southern Illinois and Kentucky.
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Magnitude 3.7 EASTERN KENTUCKY
Friday, September 17, 2004 at 15:21:43 UTC
Preliminary Earthquake Report
U.S. Geological Survey, National Earthquake Information Center
World Data Center for Seismology, Denver

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Magnitude |
3.7 |
| Date-Time |
Friday,
September 17, 2004 at 15:21:43 (UTC) - Coordinated Universal Time
Friday, September 17, 2004 at 11:21:43 AM local time at epicenter
Time
of Earthquake in other Time Zones |
| Location |
36.93N 84.01W |
| Depth |
1.2 kilometers |
| Region |
EASTERN KENTUCKY |
| Reference |
45 km (25 miles) NW of Middlesboro,
Kentucky
55 km (35 miles) ESE of Somerset, Kentucky
80 km (50 miles) WSW of Hazard, Kentucky
160 km (100 miles) SSE of FRANKFORT, Kentucky
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| Source |
CERI |
| Remarks |
mbLg 3.7 (GS). Felt (V) at
Gray; (IV) at Barbourville, Corbin, London and Rockholds; (III) at
Manchester and Williamsburg. |
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Mild earthquake rattles Central Indiana
No damage or injures reported from the 3.6 magnitude quake
By Stuart A. Hirsch
September 13, 2004
A minor earthquake jostled Central Indiana awake Sunday, shaking
some buildings but causing no damage or injuries.
The 3.6 magnitude earthquake was recorded at 8:05 a.m., and was
the state's first in more than two years. Its epicenter was located about seven
miles north of Shelbyville, according to the U.S. Geological Survey.
Scientists who study the earth said the incident was not tied to
any major fault lines and did not signal more temblors to come.
Hoosiers as far north as Noblesville, as far west as
Martinsville and Brownsburg and as far east as Rushville found themselves
asking, "Was that what I think it was?"
"It didn't last long, but it sure did wake us up,"
said Julie Jones, a dispatcher at the Shelby County Sheriff's Department.
"Our consoles were shaking and as soon as it stopped all the lines lit
up."
Tim Cooney, a mortgage banker who lives about two miles north of
Shelbyville, thought it was another of the many National Guard helicopters that
fly over his house.
The Shelbyville Armory next to the Shelbyville Airport is home
to an aviation support facility.
Perhaps there was a crash, he thought.
"My wife felt the bed swaying, and she knew right away it
was an earthquake," Cooney said. "I thought my wife was off her
rocker."
Jason Adams, an advertising manager who lives in an apartment
complex on the Northeastside, thinks his dogs Jake and Mazzy felt the quake
coming. They woke up and started barking about 7:55 a.m.
"They just wouldn't stop," he said. "And the next
thing I knew, there was a shock wave that went through the building. I could
feel the whole building move."
Gary Pavlis, a professor of geological sciences at Indiana
University, said the state experiences minor quakes every few years.
Sunday's earthquake occurred about six miles deep, he said, in
an area of structures geologists don't understand well. He said the shaking
likely was set off when a rock roughly the size of a good-sized building -- say,
six or seven stories tall -- shifted.
According to the US Geological Survey, about 130,000 earthquakes
with a magnitude of 3 to 3.9 occur every year.
In 2003, there were 1,300 earthquakes in that magnitude range in
the United States, according to statistics compiled by the geological survey.
The most recent earthquake in the region occurred June 28, near
Troy Grove, Ill. That temblor had a magnitude of 4.2, according to the
geological survey's Web site.
The last recorded earthquake in Indiana occurred on June 18,
2002. The temblor registered a magnitude of 5.0 and was centered near Darmstadt,
about 10 miles north of Evansville. It caused little damage.
While there have been major earthquakes in Indiana territory
over the past 20,000 years, Pavlis said, the chances of experiencing "the
big one" are far less likely than in California.
"That's the perspective that people have to keep in
mind," Pavlis said. "This is one of those small events that just pop
off now and again that can't be related to any specific geological structures or
faults."
Star reporter John Strauss contributed this story.
Call Star reporter Stuart Hirsch at (317) 444-2805.
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Date-Time - 2002 06 18 17:37:13 UTC
Location - 38.07N 87.68W
Depth - 5.0 kilometers
Magnitude - 5.0
Region - SOUTHERN INDIANA
Reference - 10 miles (15 km) NW of Evansville, Indiana
Source - USGS NEIC
The following is a release by the United States Geological Survey, National Earthquake Information Center: A moderate earthquake occurred IN SOUTHERN INDIANA about 10 miles northwest of Evansville at 11:37 AM MDT, Jun 18, 2002 (12:37 PM CDT in Indiana). The magnitude and location may be revised when additional data and further analysis results are available. The earthquake was felt in parts of Illinois, Indiana, Kentucky, Missouri, Ohio and West Virginia. No reports of damage or casualties have been received at this time.
Quake hits Indiana along New Madrid Faults
This earthquake was widely felt including initial reports from as far away as West Virginia. The earthquake caused only minor damage in the immediate area of the event. The USGS has received reports of minor damage including broken glass, objects thrown off of shelves, and cracked chimneys. No injuries have been reported.
The earthquake occurred in one of the more seismically active portions of the United States east of the Rocky Mountains. A large area covering southern Illinois, southwestern Indiana, and parts of western Kentucky and southeastern Missouri has earthquakes rather frequently, by eastern U.S. standards. Most years, this area has a few earthquakes large enough to be felt, but, on average, damaging earthquakes occur about once a decade. The largest earthquakes from this region in the twentieth century were the magnitude 5.5 southern Illinois earthquake of November 1968 and the magnitude 5.2 southern Illinois earthquake of June 1987. The magnitude 3.9 southern Indiana earthquake of December 7, 2000 had an epicenter very near that of today's shock. This seismicity is north and northeast of the well-known New Madrid seismic zone, which is in the bootheel of southeastern Missouri and adjacent Arkansas and western Tennessee. The earthquake occurred within the generally stable interior of the North American plate, far from currently active plate boundaries. The modern earthquakes in this part of the U.S. are thought to result from the reactivation of ancient faults, which are being squeezed by stresses from the modern motion of tectonic plates. Previous earthquakes in this area have not been associated with movement on specific geologically mapped faults.
In the past 10 years, geologists working in the area have found evidence of prehistoric earthquakes in the Wabash River Valley that were probably much larger than any historical earthquakes. Geologic evidence indicates that these prehistoric earthquakes occurred several thousand years ago.
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The New Madrid Fault System extends 120 Miles southward from the area of Charleston, Missouri, and Cairo, Illinois,
through New Madrid and Caruthersville, following Interstate 55 to Blytheville and on down to Marked Tree, Arkansas.
It crosses five state lines and cuts across the Mississippi River in three places and the Ohio River in two places.
The Fault is Active, averaging more than 200 measured events per year (1.0 or more on the Richter scale), about
20 per month. Tremors large enough to be felt (2.5-3.0 on the Richter scale) are noted annually. Every 18 months
the fault releases a shock of 4.0 or more, capable of local minor damage. Magnitudes of 5.0 or greater occur about
once per decade, can do significant damage and be felt in several states.
The highest earthquake risk in the United States outside the West Coast is along the New Madrid Fault. Damaging
temblors are not as frequent as in California, but when they do occur, the destruction covers over more than 20
times the area because of underlying geology.
A damaging earthquake in this area (6.0 or greater) occurs about every 80 years (the last one in 1895). There
is a 50% chance of such a quake by the year 2000. The results would be serious damage to schools and masonry buildings
from Memphis to St. Louis.
SEMA - MISSOURI STATE EMERGENCY MANAGEMENT ASSOCIATION
MISSOURI - SEISMIC SAFETY COMMISSION
ENGLISH HILLS FAULTS
The English Hills faults are located on the southeast flank of the Benton
Hills in Scott County, Missouri. Originally described by geologists in the 1930s, the faults had been ignored for
decades: their very existence had even been challenged.
First the material displaced by faulting in the trenches is quite young geologically. It appears that, while
8 to 12 feet of vertical displacement has occurred at the trench site, most of the displacement is horizontal---how
much horizontal displacement is not yet known. Modern soil profiles, which are usually less than 10,000 years old,
have apparently been displaced by large earthquakes along the English Hills faults. Faulting within the past 10,000
years is considered "active." It must be assumed that active faulting will continue in the future.
NEW MADRID FAULT SYSTEM MAP
THE 1968 QUAKE IN ST. LOUIS
THE COMMERCE FAULT OF ILLINOIS
QUAKE EXPECTATIONS IN ILLINOIS
A REBIRTH OF THE ILLINOIS BASIN
NORTHERN
ILLINOIS EARTHQUAKES - TEXT
NORTHERN ILLINOIS EARTHQUAKES - PDF -
WITH MAPS
MINNESOTA EARTHQUAKE HISTORY
NEIC - MAP SITE
WISCONSIN EARTHQUAKE HISTORY
IOWA NOT PREPARED FOR BIG QUAKES
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