From the July 2015 Desktop News | Since November 2014, 15 earthquakes have occurred in Alabama’s Greene County, located just southwest of Tuscaloosa County. This outbreak of seismic activity has local geologists stumped, with no clear cause in sight.
The Geological Survey of Alabama has released a news report with the latest information on the earthquakes, informing the public that these earthquakes have not been powerful, topping out at a magnitude of 3.8 on the Richter scale.
“None of them have been very big, and there’s no real indication that, you know, ‘the big one’s on the way,’ so from a community and safety perspective these aren’t anything that people need to worry about,” said Dr. Samantha Hansen, Assistant Professor in the Department of Geological Sciences. “I used to live in California, and they have these there all the time. It’s just the fact that we’re having so many of them and that we’re in Alabama that is making people worry, and understandably so.”
In many places around the country, mining activity and hydraulic fracturing, also known as fracking, has been blamed for unexpected seismic activity in areas not usually prone to it. This is not the case in Greene County, according to Hansen.
“I’ve talked to quite a few people at the [Alabama] Geological Survey, and as far as I can tell, there’s no real activity going on in that area as far as mining, fracking, or water injection that would lead to what you would call an induced earthquake, meaning manmade,” Hansen said. “The nearest activities that could potentially cause these kinds of events are about 30 miles away, and you aren’t going to induce earthquakes this small with activity from that far away.”
So, if the earthquakes aren’t caused by humans, what is the cause? The recent installation of a new seismic monitoring station by the University of Memphis may help to provide answers, but until more information comes in the best our geologists can do is offer potential explanations.
“The world is a very dynamic place, shifting all the time, and there may be some kind of stress change that has reactivated these faults and caused them to start popping off little earthquakes again,” Hansen said. “Northwest of here, closer to Memphis, there is the New Madrid [Seismic Zone] which is known for having a lot of seismic events. It’s a bit far south by comparison, so if [the local earthquakes] are related to that tectonic structure, we don’t really know.”