Sunday quake packed more bark than bite

By Jesse Campbell (jesse.campbell@mountaintimes.com)



Article Published: Aug. 28, 2013 | Modified: Aug. 28, 2013

As Dr. Scott Marshall, a geophysicist at Appalachian State University, compared the frequency of earthquakes in the southeastern United States to the seismic activity in the rest of the world, he gave some insight to Sunday’s 2.9-magnitude quake in Blowing Rock.

During Monday alone, Marshall said multiple 4.0-magnitude occurrences occurred across the globe, including a 4.6 in China and a 5.1 in Russia.

“There is a 5.0 magnitude earthquake everyday in the world,” Marshall said. “This particular quake was felt relatively strongly because the focus was very shallow. This one had one of about 5.6 miles deep.”

Marshall said the Southern Appalachians typically experience two or three quakes of this magnitude every year.

Approximately 40 seismic events happen in the eastern United States per year, Marshall said.
“If anyone out West was to read this article, they would probably laugh at a 2.9,” Marshall said.

But that is to not downplay the event, he added.

“It’s unlikely this is a precursor (to a bigger event), but it’s possible,” he said. “There is nothing peculiar about a 2.9 in the Southern Appalachians, but it doesn’t mean we won’t have a 7.0 in magnitude the next day.”

While the region’s seismic activity is spotty compared to the Western United States, earthquakes have wreaked regional havoc before.

One of the more widely discussed quakes is the 5.6 event that happened in Giles County, Va., in 1897. There was also the infamous 7.3 Charleston, S.C., quake in 1886.

Marshall said seismology is still an emerging field, making it difficult to pinpoint the exact cause of a quake.

“It’s like the weather,” he said. “At the end of the day, a weatherman has a lot of data. If he wants to know what the temperature is in the atmosphere, he can send up a balloon, but imagine if you are living in a cave deep inside the earth. You have never seen the sky before; you have no instruments up there, but you are supposed to be able to predict the weather. That is the problem with earthquakes. It is a very complicated and difficult science.”

Sunday’s event was not as carefully documented compared to similar quakes out West.

“Unfortunately when you look at a map of the United States, all the seismometers are out West,” Marshall said. “Only 14 permanent ones really observed it. If it had happened out West, it would have been recorded by hundreds of seismometers.”

According to the U.S. Geological Survey, moderately damaging earthquakes strike the inland Carolinas every few decades, and smaller earthquakes are felt about once each year or two.
Earthquakes in the central and eastern U.S., although less frequent than in the western U.S., are typically felt over a much broader region. The largest earthquake in the area (magnitude 5.1) occurred in 1916, according to the USGS.

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