West Alabama Earthquakes
June 30, 2015
Two More Quakes Recorded in Greene County Bringing Total to 16 over 8 Months.
More earthquakes have shaken northwestern Greene County, an area located approximately 30 miles southwest of Tuscaloosa.
[caption id="attachment_379" align="alignright" width="300"] Greene County has experienced 16 earthquakes within the last eight months. (Source: U.S. Geological Survey)[/caption]
The latest quakes, according to he United States Geological Survey, included a magnitude 2.1 earthquake which occurred 11 miles SSE of Aliceville late Monday, June 29. About three-and-a-half hours later, a stronger and deeper earthquake occurred a few miles southeast of the first one, with a magnitude of 3.8 and a depth of five kilometers. The USGS reports that the epicenter was located about 20 kilometers northwest of Eutaw. No damage or injuries were reported.
16 quakes have now shaken a pocket of northwestern Greene County within a span of about eight months, and geologists and researchers are still trying to determine the exact cause.
"The cause and location of the earthquakes is several kilometers below the earth's surface," Sandy Ebersole of the Geological Survey of Alabama wrote in an email to AL.com. "Given this, it can take significant time gathering seismic, geologic data, and maps to help us investigate and interpret the driving mechanism.”
The second earthquake was also the strongest earthquake to occur since a magnitude-3.8 quake happened on November 20, 2014.
"We do know that clusters of earthquakes occur from time to time as part of normal seismic activity in our dynamic planet," Ebersole told AL.com. "These clusters often go unnoticed, but are of interest to those studying geology and seismology as they can teach us more about fault movement, subsurface structures, and stress in the crust. These earthquake clusters or swarms are very rarely followed by a large magnitude earthquake."
In April, Ebersole spoke to the citizens of Greene County in a meeting held by the Greene County Emergency Management Agency in Eutaw to explain the recent earthquakes, according to the Greene County Democrat. Ebersole said that there are a series of fault lines deep underground that have been covered by thousands of years of geologic activity. Two of the same fault lines are from the Southern Appalachian Mountains and run close to the surface near Fort Payne in Northeast Alabama. According to the graphic, several of the fault lines intersect along and just south of where many of the most recent earthquakes have occurred.
[caption id="attachment_384" align="alignright" width="300"] A series of fault lines runs through Greene County, Alabama (Source: ESRI via Greene County Democrat).[/caption]
A dynamic map of the earthquakes provided by the U.S. Geological Survey can be found here.