By Dave Russell
The ground just southeast of Whittier was shaking, rattling and rolling last week as a series of earthquakes struck. The biggest, a 2.5 temblor Wednesday night at 11:03 p.m., was felt and heard by citizens across Jackson County.
“We felt the house shake,” Mary Helen Clement said on Facebook. “Windows and doors rattled. We live in Whittier.”
Charlie Jones, also of Whittier, said he heard “a big boom that sounded like an explosion going off behind our house.”
“I heard what sounded like far away thunder,” Kathie McCoy said. “And my blinds on my windows shook. I’m in the Cherokee area.”
Martha Patterson heard the booming on Rufus Robinson Road in Dillsboro, she said.
The U.S. Geological Survey says six earthquakes struck between Saturday, Sept. 7, and Wednesday, Sept. 11. All were centered around the split of U.S. 441 northbound from U.S. 74 in the Qualla area.
The first to hit was a magnitude 1.9 earthquake centered near Bumgarner Branch at 8:14 p.m. Saturday night.
On Monday, at 4:21 a.m., a 1.4 magnitude earthquake struck near Crooked Creek.
Later Monday, at 3:08 p.m., a 2.0 struck near the John A. Crowe sports complex.
The first of three Wednesday temblors was a 2.3 magnitude at 8:13 p.m. centered near the intersection of Pinecrest Drive and U.S. 441.
The biggest was the 2.5 at 11:03 p.m. Wednesday, about 500 yards southwest of the previous one, just across the Tuckaseigee River.
About 10 minutes later, a 2.1 struck about half a mile northwest of that one, between Thomas Valley Road and the Tuckaseigee River.
A small series of earthquakes in a close geographical area is referred to as a “swarm,” according to John Bellini, a geophysicist with the USGS National Earthquake Information Center.
“They’re more common in California, for example, but the eastern United States does have swarms from time to time,” he said. “You might have a series of events that go on for a few days or even a few weeks and then no seismic activity for a while. There’s a small fault in the area that is moving.”
There are no major faults, such as the San Andreas fault that causes earthquakes in California, he said.
“It’s not something I would worry about in terms of there being a large earthquake or these being foreshocks building up to one,” he said. “We can’t predict earthquakes, but I wouldn’t expect something even in the mid-three range. That’s not to say it can’t happen. I don’t know if this will continue or if this is all we can see.”
USGS earthquake data
Since at least 1776, people living inland in North and South Carolina have felt small earthquakes and suffered damage from infrequent larger ones. The largest recorded earthquake in the area was a 1916 magnitude 5.1 near Asheville.
Moderately damaging earthquakes strike the inland Carolinas every few decades and smaller earthquakes are felt about once each year or two.
A magnitude 4 eastern U.S. earthquake typically can be felt at many places as far as 60 miles from where it occurred, and it infrequently causes damage near its source.
Most bedrock beneath the inland Carolinas was assembled as continents collided to form a supercontinent about 300-500 million years ago, raising the Appalachian Mountains. Most of the rest of the bedrock formed when the supercontinent drifted apart about 200 million years ago to form what are now the northeastern United States, the Atlantic Ocean and Europe.
At well-studied plate boundaries like the San Andreas fault system in California, scientists can often determine the name of the specific fault responsible for an earthquake. This is rarely the case east of the Rocky Mountains.
The inland Carolinas region is far from the nearest plate boundaries, which are in the center of the Atlantic Ocean and in the Caribbean Sea. The region is laced with known faults but numerous smaller or deeply buried faults remain undetected. Few, if any, earthquakes in the inland Carolinas can be linked to named faults.