What is the greatest earthquake threat to Ohio?
Many seismologists and emergency planners consider the New Madrid, Missouri seismic zone to pose the greatest threat to Ohio, particularly the greater Cincinnati area of southwestern Ohio. The great earthquakes in the New Madrid zone, from December, 1811 through February, 1812, are thought to have had magnitudes in the 7-8 range. They were strongly felt throughout most of Ohio and caused chimneys to fall in Cincinnati. It is difficult to evaluate the effects that a recurrence of these earthquakes would have on Ohio today. In 1811, much of Ohio was still a wilderness and the population was about 40,000. Cincinnati was the largest town in Ohio, with about 2,500 residents. The dense population, infrastructure, and abundance of older, non-reinforced masonry buildings in southwestern Ohio would contribute to the vulnerability of the area. Structures built on unconsolidated valley-fill sediments would be particularly vulnerable because of the tendency of these sediments to amplify ground motion.
The threat from seismic zones in Ohio is difficult to assess because the historical record is so short. We know that the Western Ohio (Anna) Seismic Zone and the Northeastern Ohio Seismic Zone can produce earthquakes in the 5 magnitude range and some seismologists suggest that each of these zones could produce earthquakes at least one whole magnitude or more larger. Such earthquakes would probably produce significant damage.
It is an interesting speculation to consider our perception of the New Madrid Seismic Zone if the great events of the early 1800's had occurred a century earlier, when there was no significant European settlement in the Midwest. It is probable that eastern settlements would have noted a slight shaking and Native Americans in the area may have had oral accounts of great earthquakes in the past. Geologists would have noted surviving topographic features suggesting great upheaval; however, without the many first-person accounts recorded during the New Madrid sequence, we would probably not interpret these earthquakes to have been so large and the public would not perceive them as indicative of a significant threat.
Last update July 20, 2005