Here in the Tennessee Valley, earthquakes don’t occur every day but they are certainly not uncommon. The majority of the time, when an earthquake happens here, the magnitude is low and not felt. Areas that commonly see earthquakes are regions right along a fault line; for example, California on the San Andres Fault. Although our region doesn’t reside directly over a fault line we still experience earthquakes.

In northern Alabama, earthquakes are associated with the Southern Appalachian Seismic Zone while southern Alabama is impacted by the Bahamas Fracture Seismic Zone. Just to the northwest, there is the New Madrid Fault, this impacts portions of Arkansas, Illinois, Indiana, Kentucky, Mississippi, Missouri, and Tennessee.

An earthquake’s magnitude is measured on the Richter scale, which was developed in 1935. The magnitude of an earthquake is determined by the amplitude of waves recorded on a seismograph. Magnitude on the scale ranges from 0 to 10, with 10 being the highest. The earthquakes in Alabama range from 2.5 to 5.4, keeping it in the minor earthquake category. In this category damage that is reported is generally minimal and it is able to be felt.

When looking at the statistics for northern Alabama the area has experienced 37 earthquakes; this is based on magnitude 2.5 earthquakes or higher. This range was chosen because anything below 2.5, although detectable, is harder to feel. Data was examined from 1950 to the present day, using information from the United States Geological Survey (USGS). Here in northern Alabama, the average earthquake has a 3.0 magnitude.

The strongest earthquake here in our viewing area was felt in DeKalb County. On April 29th, 2003, 4.6 magnitudes were detected 5 miles south of Valley Head. The epicenter of this quake was centered within DeSoto State Park and is likely where the most intense shaking occurred. According to the USGS, just over 17,000 individuals reported feeling the earthquake.

Looking at the entire state of Alabama, there have been a good amount of earthquakes from 1950 to the present. There have been a total of 163 2.5 or greater magnitude earthquakes. Some of these quakes were associated with mine explosions, mine collapses, or other types of explosions.

The strongest quake was measured at magnitude 4.8, this occurred twice. The first 4.8 magnitude quake was in 1997, nine miles north-northwest of Flomaton in the southern portions of the state. The second was just to the west of Birmingham near the community of North Jones in 1999.

Saturday’s Earthquake

Early Saturday morning, August 14th, some viewers had a shakey start to their day. A magnitude 2.7 earthquake rocked portions of northern Madison County during the predawn hours. The epicenter of this earthquake was 3.7 miles northwest of the Hazel Green community.

You can read more about this earthquake here.