Tuesday, September 24, 2019

The New Madrid Earthquake of 1811-1812 Research Paper

The New Madrid Earthquake of 1811-1812 - Research Paper Example Giant waves rose up and swept north giving the impression it was flowing backwards. Boats along the river were engulfed, capsized and their crew drowned. They were many unusual factors about the New Madrid Earthquake of 1811-1812. The first surprising was their location. They were centered at the southeast corner of Missouri far from the active seismic zones of the mountain chains on the edges of the continents, which are the boundaries of tectonic plates. Secondly, their magnitudes were unusually high; in the range of between 8.1-8.3 on a Richter scale. Thirdly, the pattern was unusual in that there were three shocks of about the same magnitude separated by weeks at a time. As mentioned before, the first one occurred on December 16, 1811, with an 8.2 magnitude at 2:00 am. The second one occurred January 23, 1812 at an undisclosed time with an 8.1 magnitude and the third one occurred February 7, 1812 with the highest recorded magnitude of 8.3 at 3:15 am. The impact of that this disas ter had on victims far and near was indescribable and sad to say possibilities of it happening again is a certainty! What is New Madrid Seismic Zone? With reference to cusec.org the New Madrid Seismic Zone (NMSZ) is the most active seismic area in the United States east of the Rocky Mountains. The NMSZ is located in southeastern Missouri, northeastern Arkansas, western Tennessee, western Kentucky and southern Illinois. Southwestern Indiana and northwestern Mississippi are also close enough to receive significant shaking from large earthquakes occurring in the NMSZ. Analysis of the New Madrid Seismic Zone The active faults in the NMSZ are poorly understood because they are not expressed at the ground surface where they can be easily studied. The faults are hidden beneath 100- to 200-foot thick layers of soft river deposited soils called alluvium. Fault scraps and traces in the soft alluvium erode in a very short time or may be rapidly covered by new deposits thereby quickly hiding ev idence of earthquake fault lines. Faults in places like California, where rocks are at or near the ground surface, are much easier to study because the faults are readily found, seen, measured and analyzed. (Cited from cusec.org) Knowledge about some of the NMSZ faults is obtained by seismograph recordings of the frequent small earthquakes. St. Louis University, University of Memphis, the U.S. Geological Survey and University of Kentucky operate more than 30 seismograph stations to monitor earthquake activity in the NMSZ and Central U.S. Micro seismic earthquakes (magnitude less than 1.0 to about 2.0), measured by seismographs but not felt by humans, occur on average every other day in the NMSZ (more than 200 per year). The measured locations of micro seismic earthquakes show some trends that have been used to identify active faults in the NMSZ. The trends indicate a four-segment, zig-zag fault system with a total length of about 125 miles stretching from Marked Tree, Arkansas north eastward through Missouri, Tennessee and Kentucky to Cairo, Illinois. In the past 25 years, scientists have learned that strong earthquakes in the central Mississippi Valley are not freak events but have occurred repeatedly in the geologic past.   Earthquakes in the central or eastern United States affect much larger areas than earthquakes of similar magnitude in the western United States.   For example, the San Francisco, California, earthquake of 1906 (magnitude 7.8) was felt 350

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