Three earthquakes from the New Madrid fault hit the United States during the years 1811 and 1812. These earthquakes are considered some of the largest earthquakes the United States has ever known ("Largest..."). They are estimated to have had a magnitude of 8.0 or higher. If you will remember, most earthquakes you hear about these days are between 6.0 and 7.0. (In 1994 the 6.7 in Northridge, CA and in 1995 the 6.9 in Kobe, Japan are two examples) (Gomberg et al.). Due to the 1811-12 earthquakes, "[l]arge areas sank into the earth, new lakes were formed, the course of the Mississippi River was changed, and forests were destroyed over an area of 150,000 acres..." ("The Great New..."). These earthquakes were obviously not a small ordeal. Not only was damage recorded in the immediate area around the New Madrid fault, but South Carolina and Washington DC had their share as well. In addition, bells were heard ringing in Boston, hundreds of miles from the epicenter, the beginning of the earthquake (Gomberg et al.).
The above map shows the areas affected by the 1811-1812 earthquakes and their intensity, which is denoted by the roman numerals (http://wwwneic.cr.usgs.gov/neis/eqlists/USA/1811-1812_iso.html)
This large range of area impacted by these earthquakes is much larger then any in California. The reason for this is a difference in geology in the two areas. In the middle United States there are several layers upon layers of water saturated sand covering it. It is for this reason that these earthquakes caused so much more damage ("large surface displacements, sand blows, fissures and landslides") in a much larger area then they would have in California (Nuttli). Not only did they have a large effect on the land, but these earthquakes also had a large impact on the people who had settled this area in the early ninteenth century. It is said that people took these earthquakes as a sign from God and quickly took to church (Bond). Many diary entries and newspaper articles decribe what took place over the many months that the aftershocks contnued for (Andreassen). It is also said that after the earthquakes many settlers moved out and the area was sparse with people because others new of its reputation amd stayed away (Wyllie).
An illustration of the damage caused by the 1811-12 earthquakes (http://quake.wr.usgs.gov/prepare/factsheets/NewMadrid/Woodcut.gif).
Luckily, during the time of these massive earthquakes there were relatively few settlements this far west, so the loss of human lives and property damage were very low. This is not the case now. The New Madrid fault runs between St. Louis, MO and Memphis, TN and little has been done to prepare these large cities, let alone the varies smaller cities and towns surrounding the area, to sustain an earthquake of this size or even a smaller one. Even scarier to think about is that most scientists believe it is very likely that within the next 50 years another earthquake of at least a magnitude of 6.0 will hit the New Madrid fault. Even an earthquake of this magnitude could cause serious damage and great loss of life if little is done in the near future to protect surrounding cities (Gomberg et al.).
The area in red shows the New Madrid fault (or seismic zone) in relation to the topography of the area (http://showme.net/~fkeller/quake/topog.htm).  

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