The Earthquakes Of 1811 And 1812 In

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The Earthquakes Of 1811 And 1812 In The Mississippi River Valley Essay, Research Paper When one thinks of earthquakes, the Mississippi river valley (MRV), does not frequently come to mind. One usually thinks of one of California’s numerous faults or somewhere in Alaska. However, little known to the general public, there were two massive earthquakes in the MRV, which rank among the top three in the contiguous United States and in the top ten for the entire United States (http://wwwneic. cr.usgs.gov/neis/eqlists/bigten.lis). Starting in the early morning hours of December 16, 1811 a violent shaking of the earth began, which continued on for three months, producing two of the three largest quakes in the contiguous US, this particular quake registered an 8.0 in magnitude on the

Richter scale. There was a second quake on February 7, 1812 which registered 8.2 (http://wwwneic.cr.usgs.gov/neis/eqlists/ bigten.lis). The plate which is responsible for this activity is named the New Madrid Seismic zone, it is named for the only populated city that was in existence in the time and the area of these earthquakes, New Madrid, Missouri. The New Madrid Seismic zone lies in the central MRV, starting in southern Illinois and ending in southeast Missouri, western Tennessee. Usually an earthquake consists of a principal shock and then the aftershocks, the 1811-1812 earthquakes didn’t follow the usual pattern. There was the first primary shock, at and then it’s aftershocks, however the aftershocks from the first quake hadn’t subsided before the second principal

shock hit. Following suite, the aftershocks from the second quake had not terminated when the third and largest principal shock hit (http://www.eas. slu.edu/Earthquake_Center/Nuttli.1973/intensity.html). It is difficult to gage the actual intensity of the earthquakes due to the lack of technology, however, the strength can be estimated by the damage caused by the quakes and also by the journals of the people settling this part of the country. Fortunately, a man by the name of Jared Brooks, who was a resident of Louisville KY, kept a journal of the seismic activity from December 16, 1811 to May 5, 1812. He had devised his own system of measuring intensities with a set of horizontal pendulums from 1 to 6 inches in length and a set of vertical spring- mass systems. Devising his own

instruments, he also created his own categories of intensities, with six levels. The first is comparable to an eight on the Modified Mercalli scale, second level is a five to a six, third is a four to five, fourth is a three, the fifth level is comparable to a two on the MM, the sixth is a one (http://www.slu.edu/Earthquake_Center/ Nuttli.1973/Magnitudes.html). With the assistance of these measurements scientist have been able to devise approximate strengths of these earthquakes. The following is a map with the MM intensity values for the December 16, 1811 earthquake. Map (http://www.eas.slu.edu/Earthquake_Center/Nuttli.1973/Intensity.html) Through some in depth research about ground motions and intensities of these earthquakes, if has been concluded that the epicenter of the

first earthquake (December 16, 1811) was closer to the northeast Arkansas near the southern end of the lake formed by the St. Francis River. The lake in the area was raised as much as 12 ft. up higher than the surrounding country. The water in the lake was drained and replaced by white sand. It was stated by the Louisiana Gazette that the river itself rose as much as 25 to 30 feet above it’s banks (http://www.eas.slu.edu/Earthquake_Center/Nuttli.1973/Intensity.html). There are several published personal accounts of these earthquakes, the following is an collection of excerpts from a letter found in a book entitled, “Lorenzo Dow’s Journal,” published by Joshua Martin, printed by John B. Wolff, 1849, on pages 344-346. On the 16th of December, 1811, about two o’clock,