Current knowledge about the faults system within the New Madrid Seismic Zone (NMSZ) is obtained by studying seismograph recordings of the seismic waves produced by the frequent small earthquakes. Several organizations such as St. Louis University, University of Memphis and the U.S. Geological Survey (USGS) operate a network of seismograph stations to monitor earthquake activity in the NMSZ and Central United States.

Scientists use this network to record and study small microseismic earthquakes (magnitude less than 2.0) that occur on average every other day in the NMSZ.

The measured locations of microseismic earthquakes indicate trends scientist have used to identify active faults. The trends indicate a four-segment, zig-zag fault system with a total length of about 125 miles stretching from east central Arkansas northeastward through Missouri, Tennessee Kentucky and into southern Illinois.

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