The New Madrid SEISMIC ZONE

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The New Madrid SEISMIC ZONE
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• In the winter of 1811-1812, the Central
  Mississippi valley was struck by three of the
  most powerful earthquakes in U.S. history

Isoseismal map for the December 16, 1811
earthquake, first of the 1811-1812 New Madrid
series
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• On December 16, 1811, the 400 terrified residents
  of the town of New Madrid, MO were abruptly
  wakened by violent shaking and a tremendous roar
• It was the first of three magnitude 8 earthquakes
  and thousands of aftershocks to rock the region
  that winter

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• The two largest probably exceeded the size of any
  continental US earthquake
• No fewer than 18 of the earthquake events were
  felt on the Atlantic seaboard and in Washington
  DC
• The series was named after the small riverboat
  town of New Madrid, sited at the heart of
  epicentral zone, which was the largest settlement
  between St. Louis and Natchez in 1811

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Inhabitants per square mile, 1811-1812
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• New Madrid marks the intersection of three of the
  six fault segments currently illuminated by
  microseismicity and believed to be the rupture
  planes for the 1811-1812 earthquakes

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• The fault zone originated 750 million years ago,
  when the earths landmass was a supercontinent
• At that time, a constructive fault zone began to
  form, but failed
• It is now known as the Reelfoot Rift

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• Research confirms the 1811-1812 quakes cause
  fissuring, sand and water blows, landslides,
  large sunken lakes, waterfalls on the Mississippi
  River, and sunken forests

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Kentucky historical sign
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• Although earthquakes are less frequent here than
  in Western states, they effect much larger areas

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• In 1811, the Mississippi Valley was sparsely
  populated
• Today, the region is home to millions of people,
  including the cities of St. Louis and Memphis
• Most structures in the region were not built to
  withstand earthquake shaking
• Earthquake preparedness has lagged behind

Earthquakes recorded since 1974
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• Climatologist Dr. Iben Browning predicted that
  there would be an earthquake on the New Madrid
  Fault on December 3, 1990
• The prediction caused quite a stir

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sources

• Contemporary Newspaper Accounts of Mississippi
  Valley Earthquakes of 1811-1812 slu.edu 15
  January 2009 lthttp//www.eas.slu.edu/Earthquake_Ce
  nter/SEISMICITY/Nuttli.1973/nuttli-73-app.htmlgt
• Johnston, Arch C. and Eugene S. Schweig. The
  Enigma of the New Madrid Earthquakes of
  1811-1812. Earth. 24 (1996) 339-384.
• The Mississippi Valley Whole Lotta Shakin
  Goin On usgs.gov 15 January 2009
  lthttp//quake.wr.usgs.gov/prepare/factsheets/NewMa
  drid/gt
• Uncovering Hazards of the Mississippi Valley
  usgs.gov 15 January 2009 lthttp//quake.wr.usgs.gov
  /prepare/factsheets/HiddenHazs/gt