New Madrid Fault Zone: Geologists Predict 90% Chance of 6.5 to 7.0 Earthquake Within Next 50 Years

New Madrid Seismic Zone: Scene of Three Massive Earthquakes Just Two Hundred Years Ago

Roman numerals indicate estimated Modified Mercalli intensities for a 6.5 magnitude earthquake. (Based on maps in W. Atkinson, 1989, The Next New Madrid Earthquake, Southern Illinois University Press.)
-Iowa DNR Geological Survey

The recent 7.0 Haiti earthquake and its subsequent aftershocks-a 6.1 struck Haiti today at 6:03 AM, 35 miles WNW of Port Au Prince at a depth of 6.2 miles-highlight the severity of sudden devastating earthquakes in somewhat surprising locales, at least to the general public. One location, the Central Mississippi Valley, the scene of a series of four massive earthquakes which occurred almost two hundred years ago and which geologists predict a 9-in-10 chance of a magnitude 6 to 7 quake occurring within the next 50 years.

From the Iowa Department of Natural Resources:

The strongest historic earthquakes in North America occurred as a series of four shocks along the New Madrid Fault Zone between December 16, 1811 and February 7, 1812 and were centered near the town of New Madrid, in the boot-heel area of Missouri. Based on historic eyewitness accounts, scientists have estimated the intensity of the earthquakes using the Modified Mercalli Scale and estimated an equivalent Richter magnitude of 8.3 to 8.7. These devastating earthquakes were felt from the Atlantic seaboard to the Rockies and felled trees, opened fissures, destroyed log buildings, erupted sand and water, created Reelfoot Lake in western Tennessee, and reportedly caused the Mississippi River to temporarily reverse flow in places. Because of the low population density, fatalities were relatively few with most occurring on or near the Mississippi River.

The odds that another devastating quake could occur in the New Madrid Fault Zone in the near future? According to the United States Geological Survey, or USGS, fairly high:

Another earthquake as powerful as the great quakes of 1811-12 may not occur for many years. However, scientists estimate that there is a 9-in-10 chance of a magnitude 6 to 7 temblor occurring in the NMSZ within the next 50 years. Because of differences in the geology east and west of the Rocky Mountains, the effects of a magnitude 7 quake in the midcontinental United States could be far worse than those of the 1989 magnitude 7 Loma Prieta, California, earthquake. That quake, which struck the San Francisco Bay region during the World Series, killed 63 people and caused $6 billion of property damage.

More from the Iowa DNR, which predicts a 90% chance of a 6.0 by 2040:

Seismologists attempt to forecast earthquake size and frequency based on data from previous events. In the New Madrid Fault Zone, this analysis is difficult because there are few historic moderate to large earthquakes, and the active faults are too deeply buried to monitor effectively. Based on recurrence intervals for small earthquakes, scientists estimate a 40 to 63 percent chance of a Richter magnitude 6.0 earthquake between 1985 and 2000, rising to a 90 percent chance by 2040. Estimated recurrence intervals for larger earthquakes, approaching the size of the 1811-1812 events, vary from about 175 years to greater than 700 years.

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