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Subject: Fwd: USGS Press Release -- Scientists Update New Madrid Earthquake Forecasts
Date: Mon, 13 Jan 2003 18:21:38 EST
Thought the group might be interested in this.
Thought the group might be interested in this.
U.S. Department of the Interior
U.S. Geological Survey
January 13, 2003 Eugene Schweig
3876 Central Ave . schweig@........
Suite 2 jgomberg@........
Memphis, TN 38152
Scientists Update New Madrid Earthquake Forecasts
Scientists from the U.S. Geological Survey (USGS) and the Center for
Earthquake Research and Information at the University of Memphis have
updated their expectations for earthquakes in the New Madrid Seismic Zone.
The new forecasts estimate a 7 to 10 percent chance, in the next 50 years,
of a repeat of a major earthquake like those that occurred in 1811-1812,
which likely had magnitudes of between 7.5 and 8.0.
There is a 25 to 40 percent chance, in a 50-year time span, of a magnitude
6.0 or greater earthquake.
The earthquake probabilities in this region have changed considerably since
the most commonly cited forecast published in 1985. The new probabilities
show an increased chance of larger (7.5-8.0 magnitude) earthquakes and a
lesser chance of magnitude 6.0 and greater earthquakes. Meanwhile,
estimates of the hazard, or potential for damage caused by shaking, have
changed much less. A fact sheet with the new information is available on
the web at: http://pubs.usgs.gov/fs/fs-131-02/.
"More than fifteen years of research has given us the information to allow
us to update our forecasts. But even though the chances of a mid-sized
earthquake are reduced, the chances of a devastating earthquake in the
region have risen," said USGS scientist Eugene Schweig. "Given this new
information, people should absolutely not drop their guard. The threat of
an earthquake to Mid-America is still very real."
The New Madrid seismic zone is an area of frequent small earthquakes that
stretches along the lower Mississippi Valley from just west of Memphis,
Tennessee into southern Illinois. It also was the location of a sequence
of three or four major earthquakes in 1811 and 1812.
Major earthquakes in the range of magnitude 7.5 to 8.0 are capable of
causing widespread damage over a large region. Magnitude 6.0 earthquakes
can cause serious damage in areas close to the earthquake's epicenter
because the hazard (chance of damage in a given area) depends not only on
earthquake size, but also on where the earthquakes occur and local soil
In Memphis and throughout the Mid-America region, the USGS is improving its
earthquake monitoring and reporting capabilities through the Advanced
National Seismic System (ANSS), a nation-wide network of modern strong
motion seismometers that can provide emergency-response personnel with
real-time "shaking" information within minutes of an earthquake.
ANSS stations assist emergency responders within minutes of an event
showing not only the magnitude and epicenter, but where damage is most
likely to have occurred.
Ten new ANSS instruments were recently installed in the Memphis area, 20
have been installed across the mid-America region, and more than 175 have
been installed in other vulnerable urban areas outside the central U.S. to
provide real-time information on how the ground responds when a strong
"The ultimate goal of ANSS is to save lives and ensure public safety," said
Dr. John Filson, U. S. Geological Survey (USGS) Earthquake Program
Coordinator. "This information, already available in Southern California,
is generated by data from seismic instruments installed in urban areas and
has revolutionized the response time of emergency managers to an
earthquake, but its success depends on further deployment of instruments in
other vulnerable cities."
In 1997, during the reauthorization of the National Earthquake Hazards
Reduction Program, Congress asked for an assessment of the status and needs
of earthquake monitoring. The result was the authorization of ANSS to be
implemented by the USGS. The system, when fully implemented, would
integrate all regional and national networks with 7,000 new seismic
instruments, including 6,000 new strong-motion sensors in 26 at-risk urban
areas. To date, approximately 350 instruments have been installed
New USGS National Seismic Hazard Maps depict these hazard or likelihood of
ground shaking. The USGS and its partners in universities and state
geological surveys are preparing more detailed hazard maps for Memphis and
other areas that include the effects of local soil conditions. For more
information see http://geohazards.cr.usgs.gov/eq/.
The goal of USGS earthquake monitoring is to mitigate risk - using better
instruments to understand the damage shaking causes and to provide
information to help engineers create stronger and sounder structures that
ensure vital infrastructures, utility, water, and communication networks
keep operating safely and efficiently.
As the Nation's science agency for natural resources, hazards and the
environment, the USGS is committed to meeting the health, safety and
knowledge needs of the changing world around us.
Public Affairs Specialist
USGS Office of Communications
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