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Some of the largest earthquakes recorded in North America have been felt in St. Louis. One reason for this is St. Louis' proximity to the New Madrid Seismic zone (or Fault) that runs through the central Mississippi Valley.
Three strong earthquakes, along with hundreds of aftershocks, occurred along the New Madrid Fault between December 16, 1811 and February 7, 1812. From eyewitness accounts and recorded property damage, scientists today believe that the earthquakes would have measured 8.0 on the Richter scale, which wasn't developed until 1935.
During these 1811-1812 earthquakes, the earth shook houses violently, river banks collapsed and trees split as fissures opened beneath them. Damage from the epicenter could be seen in five states, Missouri, Illinois, Arkansas, Kentucky and Tennessee and rumblings could be felt in as many as twenty states.
Epicenter is vertically above the hypocenter, point in the crust where a seismic rupture begins.
Richter scale in which the magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs.
Seismic wave is an elastic wave generated by an impulse such as an earthquake.
Sand boil is sand and water that come out onto the ground surface during an earthquake
Aftershocks are earthquakes that follow the largest shock of an earthquake sequence.
Seismic waves rippled across the land, traveling at about 5 miles per second, arrived, 200 miles north, in St. Louis. Sleeping residents were awaken to falling chimneys, windows rattling and houses splitting. In the flood plains along the Mississippi and Missouri Rivers the sand boiled. Aftershocks were felt all through the morning.
Since these earthquakes at least seven other major earthquakes occurred. In 1974 instruments to monitor earthquakes in this seismic zone were installed. To date over 4000 earthquakes, many of them too small to be felt, have been recorded. On April 18, 2008 St. Louisans awoke to an earthquake centered in southeastern Illinois measured at a magnitude of 5.2.
We cannot avoid earthquakes but we can lessen the fear and reduce property damage through careful preparation. Survival equipment should be stored in a safe place where it can be accessed during an emergency. Survival equipment can include:
To improve earthquake preparedness, response and recovery capabilities, the St. Louis City Emergency Management Agency goes through earthquake training and exercises with many partners such as the U.S. Army Corps of Engineers, and the Red Cross. You can be a participant that will support safety for all St. Louis citizens.
Article by: St. Louis Public Library staff