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Wednesday Morning Earthquake Felt In Transylvania - Brevard NC

 

Last updated 12/12/2018 at 3:31pm



Locals shaken awake Wednesday morning can fear not, it was just a little earthquake, hitting 4.4 on the Richter scale.

According to the U.S. Geological Survey, the quake occurred at 4:14 a.m. A second, smaller quake, registering 3.3 on the Richter scale, hit about 15 minutes later.

The quakes’ epicenters were in Decatur, Tenn., a small town located roughly halfway between Knoxville and Chattanooga.

The quakes were felt as far away as Transylvania County and Atlanta, Ga. According to Brevard College Professor of Geology Jim Reynolds, eastern Tennessee is a fairly active seismic zone, but, he said, most of the quakes register in the 3 to low 4 range.

“This is one of two active seismic zones on the East Coast,” he said. “The other is near the St. Lawrence River in Canada. I’m not really sure why the St. Lawrence River is a seismic zone. There’s something funny going on up there.”

Reynolds said the eastern Tennessee seismic zone is pretty well known, with a fault line that runs parallel to the southern Appalachian Mountains. He said that fault line is about 300 to 450 million years old.

He said geologists could tell the age of the rocks in the fault line by the fossils found in them, which are from the Pennsylvanian, or the Carboniferous period. This period of time is characterized by vast swamplands, which produced much of the coal found in the Earth today.

“My guess is closer to 300 million plus or minus a millennia,” Reynolds said.

Reynolds said that earthquakes are difficult to predict, even for seismologists. He said these eastern quakes are the result of ancient stress left over from when the Appalachian mountains formed and are probably due to erosion, which, he said, is about a 10th of a millimeter a year. He said some day the internal stress will exceed the pressure of the rocks overlying the fault, but he doesn’t think there will be a big earthquake any time soon. A measured 4.4 earthquake is the amount of energy released, and the destruction from such a quake depends on how close to the epicenter a person or structure might be.

“The Richter scale isn’t a good predictor of damage,” Reynolds said. “It’s just an energy scale, but you can use it to measure how big, or far reaching, the energy was. To assess damage, geologists and seismologists use the Mercalli Intensity Scale. But I haven’t heard of any reports of damage from this earthquake yet.”

Reynolds has been a professor at Brevard College for 20 years, although this is his last year teaching. In that span, he can remember maybe three or four earthquakes. He mentioned the Brevard fault line, which marks the boundary of the French Broad River valley, a huge fault that runs from Stone Mountain, Ga., all the way to Newfoundland, Canada.

“It’s an old tectonic plate boundary that formed initially about 450 million years ago, but it reactivated about 300 million years ago and then again 400 million years ago, but it’s pretty much been quiet since then,” he said. “I’ve heard it called the San Andreas of the East.”

According to Reynolds, there are two major faults in North America: the San Andreas on the West Coast and the Brevard fault line, which changes names a few times as it makes its way North.

“If you hike the trail along the trail heading into Pisgah National Forest from Lowe’s, the rocks go from a light color to black,” he said. “That’s the edge of the fault. The other place I have seen it is at Camp Keystone. If you walk on some of the roads in the camp, you can see the transition from solid rock to shattered rock as you hit the rock zone.”

 
 

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