Earthquakes on the rise in Northeast Alabama
October 24, 2017
Southern Torch (3845 articles)
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Earthquakes on the rise in Northeast Alabama

PHOTO: Last Friday’s earthquake that was recorded northeast of Scottsboro is the eighth reported in our area during the last two years, an increase of 100 percent from the previous two. (File Photo)

By Tyler Pruett, Managing Editor

tyler@southerntorch.com

RAINSVILLE, Ala. — Last Friday (October 20), a magnitude 2.7 earthquake struck around 8 miles northeast of Scottsboro, Alabama as recorded by the United States Geological Survey (USGS). Fort Payne also experienced a 2.2 magnitude tremor in late August, as well as a 2.6 magnitude in June and a 2.3 in March. While these quakes were not strong enough to cause significant damage, seismic activity in our area has increased significantly in both frequency and magnitude in the last four years.

By reviewing data from the USGS on recorded earthquakes for the last ten years for the DeKalb County area (Southern DeKalb County line to the Tennessee state line), the number of recorded earthquakes reported in the search area increased by 75 percent (4 reported) from October 2013-October 2015 when compared to the previous two years (Oct. 2011- Oct. 13, 1 reported) and the number has increased another 100 percent in the Oct. 2015 – present (8 reported) time frame.

The number of earthquakes reported in the Northeast Alabama area (red) has increased by 100 percent in the last two years, as compared to the previous two years. Seismic events in Georgia were excluded in the numbers, but several were reported in nearby Summerville, Lafayette, and Trion, Georgia. (USGS)

These numbers only include earthquakes of 1.5 magnitude or greater, and include a search area of northeast Alabama; from the DeKalb – Cherokee County line in the south, to the  Tennessee-Alabama line in the north. The numbers also include Scottsboro and surrounding areas. These comparisons do not include Georgia, however, several seismic disturbances were recorded across the state line and a short distance away from DeKalb and Jackson counties. In the last two years, there have been two recorded quakes in Summerville, Ga. and one reported in Lafayette.

The highest magnitude quake for the area in the last ten years was the most recent tremor that occurred near Scottsboro last Friday. The eight recorded quakes in the last two years averaged around 2.11 in magnitude and averaged 2.12 in 2013 and 2014. From 2009 to 2013, the reported tremors only averaged 1.65.

Naturally occurring earthquakes are caused mostly by the rupture of geological faults within the earth that generates seismic waves.

While there are fault lines nearby, our area doesn’t have a fault line as large as the San Andreas fault in California, which extends for 750 miles. Northeast Alabama is, however, located in the Southern Appalachian Seismic Zone, which is an extension of the East Tennessee Seismic Zone.

USGS Geophysicist Paul Caruso discussed what could be the cause of these earthquakes, where our biggest threat could originate from, and what to do if our area experiences a quake large enough to cause damage.

When asked what magnitude it requires to cause significant damage to structures and infrastructure, Caruso replied, “We don’t see significant damage until earthquakes get up to about 5.5 magnitude.”

“In the Southern United States and the Central United States, the main fault we worry about is called the New Madrid fault; it runs along the Mississippi (River), around Memphis and St. Louis,” Caruso explained. “And that has produced significant earthquakes. Especially in 1811 and 1812, we think there were three major earthquakes as large as magnitude 8.”

“Of course we didn’t have seismometers to measure quakes back then, but one way we can estimate the magnitude from back then is looking at newspapers, and turns out those earthquakes rang church bells is Boston, several hundred miles away,” Caruso explained.

When asked if anything might be causing the increase in tremors, Caruso explained that human activity may be to blame.

“We’ve had several areas in the United States where we have documented induced earthquakes caused by human activity, such as pumping high quantities of water in disposal wells. They do that in some areas where they are fracking. Here in Colorado, we had the first documented case of humans causing earthquakes, which was actually the U.S. Army here at the Rocky Mountain Arsenal in the 1960’s,” said Caruso.

The event Caruso is referring to is a series of earthquakes that erupted after the U.S. Army drilled a 12,000 -foot well to dispose of waste fluids northeast of Denver, Colorado in 1961. Over 1300 earthquakes were recorded in the area during the 1960’s after the Rocky Mountain Arsenal began injecting the waste fluids in 1962.

In 2014, the USGS published a “Long-term induced hazard,” map for the U.S., which depicts the areas which are at risk for more of these, “induced” quakes. Northeast Alabama resides in an area with a moderate to low hazard on this model.

Portion of the USGS’s 2014 Long-term Induced Hazard Map, showing northeast Alabama with a moderate to low hazard for induced seismic activity. (USGS)

As our area isn’t accustomed to seismic activity, Caruso was asked what course of action people should take in the event of a significant seismic event:

“We always tell people, the best thing you can do if you feel an earthquake is get under a desk or a table, wait until the shaking stops, and then go outside,” he replied.

“Whenever there is a major earthquake where a lot of people are killed in Mexico, people are sleeping outside for weeks afterwards. It’s because of the aftershocks…. Sometimes when a building is already weakened, an aftershock can be enough to collapse it,” Caruso explained.

Southern Torch

Southern Torch

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