While the West Coast is famous for its earthquakes, other portions of the US are also earthquake-prone. Tennessee, in particular, is more likely to see earthquakes than you may realize. There are two seismic zones that produce earthquakes in Tennessee.
The two earthquakes reported early Wednesday morning in Eastern Tennessee may have come as a surprise to some Middle Tennesseans. While the 4.4 and 3.3 magnitude quakes centered near Decatur, Tennessee in Meigs County did no major damage, they were felt by some here in Middle Tennessee.
Middle Tennessee actually sits between two different seismic zones, the New Madrid Seismic Zone and the East Tennessee Seismic Zone. The New Madrid Seismic Zone extends from Northeastern Arkansas into West Tennessee, Southeastern Missouri, Western Kentucky, and Southern Illinois. The East Tennessee Seismic Zone extends from Northeastern Alabama into Southwestern Virginia.
The quakes felt Wednesday were in the East Tennessee Seismic Zone. The known fault lines in this zone are ancient and there are no known active fault lines. Despite that, this is one of the most active seismic regions in the US with multiple small earthquakes happening throughout the year.
In the East Tennessee Seismic Zone, there have been 188 earthquakes of magnitude 2.5 or greater since measurements began in the 1970s. The strongest earthquake on record for this region was a magnitude 4.7 in Maryville, Tennessee in 1973. According to scientists, magnitude 5.0 to 6.0 earthquakes are possible every 200-300 years and earthquakes up to 7.5 in magnitude are possible in this region.
Just to our west is an area that has a history of producing large destructive earthquakes. The New Madrid Seismic Zone is responsible for some of the biggest and most devastating earthquakes east of The Rockies. The New Madrid Earthquakes are perhaps the best example of the devastation possible in this area. During the three month period between December of 1811 and February of 1812, New Madrid and surrounding areas were rocked by four devastating earthquakes with estimated magnitudes between 7.3 and 8.0. Over 80,000 square miles of fissures were left in wake of these quakes and Reelfoot Lake was formed where the ground subsided due to this seismic activity.
An earthquake of similar magnitude would be mean widespread catastrophic damage across portions of Alabama, Arkansas, Illinois, Indiana, Kansas, Kentucky, Mississippi, Missouri, Oklahoma, Texas, and particularly for us here in Tennessee.
Unfortunately, predicting exactly when and where an earthquake will happen is not a possibility yet. However, scientists can look at past data and also look at current seismic trends and determine which areas have the greatest risk for earthquake activity. The US Geological Survey maps out the areas where earthquakes are a greater hazard every 6 years.
If you take a look at the map you’ll notice that the West Coast and Alaska are the areas most prone to seismic activity. However, you’ll also notice that the New Madrid Seismic Zone and the East Tennessee Seismic Zone also show up on this map. While the threat of a devastating earthquake is higher on the west side of the state, East Tennessee still needs to be on alert.
The USGS estimates that earthquakes as large as 7.5 in magnitude are possible in the East Tennessee Seismic Zone. A for the New Madrid Seismic zone The USGS estimates that there is a 7–10% chance of an earthquake with a magnitude comparable to one of the 1811–1812 quakes within the next 50 years and a 25–40% chance of a magnitude 6.0 earthquake in the same time frame.
With Middle Tennessee in between these two active zones, preparation is key.