Comment: Caution urged in revising earthquake hazard estimates in New Madrid Seismic Zone



In the winter of 1811–1812, the central Mississippi Valley experienced three major earthquakes, known as the New Madrid sequence. Shaking was felt across central and eastern North America, and the landscape was drastically changed, including a temporary disruption of the course of the Mississippi River and the sinking of large tracts of forest land. Careful analysis of these well-documented effects and comparison with patterns of destruction from other earthquakes globally leads to the inference that the 1811–1812 events had magnitudes close to 8 [Johnston, 1996]. It has recently been reported in the scientific press and regional newspapers that new results of Global Positioning System (GPS) strain monitoring in the central United States indicate that seismic hazard is much lower than previously estimated [e.g., Kerr, 1999].