Earthquake Risk in the Central US: the New Madrid Seismic Zone

From 1-3 April 2016, RPI’s Science Program Coordinator, Dr. John Wardman, partook in the Earthquake Insight Field Trip to the central United States to learn about earthquake risk in the New Madrid seismic zone (NMSZ). The NMSZ is the most active intraplate seismic zone in North America, and has experienced major (M7-8) earthquakes roughly every 500 to 600 years for at least the past 2,400 years. The most recent large earthquake sequence of 1811-1812 was felt throughout the eastern United States and, if repeated, would pose strong shaking, liquefaction, subsidence, and flooding hazards for many now-populated urban centers in the Mississippi Valley. Based on this history of past earthquakes, the USGS estimates the chance of having an earthquake similar to one of the 1811–12 sequence in the next 50 years is about 7 to 10 percent, and the chance of having a magnitude 6 or larger earthquake in 50 years is 25 to 40 percent. This report summarizes the current knowledge on seismic hazard in the NMSZ, the potential impact to vulnerable societies in the region, and an overview of the recurrence intervals and probabilities for major NMSZ earthquakes.