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The day Kentucky shook; UK Seismologist analyzes the Tennessee earthquake

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Posted at 3:34 PM, Jan 21, 2020
and last updated 2020-01-21 15:34:15-05

LEXINGTON, Ky. (LEX 18) — Within minutes after 2:12 pm on Monday, the LEX 18 news department emails began to blow up. Viewers from Jelico up to Richmond were alerting us to the earthquake they had all felt rattle the ground beneath them.

“This was undoubtedly an earthquake,” said Dr. Seth Carpenter of the University of Kentucky’s Geological Survey.

The 3.8 magnitude quake was centered in northern Tennessee, but could be felt for nearly two hundred miles in every direction, or as far away as Atlanta as Dr. Carpenter pointed out.

So why such a broad range, given a 3.8 is not really much of a register on a Richter Scale?

“In the eastern and central U.S. the crust is thicker, colder, basically stronger,” said Carpenter.

“So there’s much less diminishment of the earthquake waves as they travel through the earth’s crust.”

Simply put: a magnitude 3.8 earthquake in this region can travel up I-75 from Tennessee with much more fervor than the waves from a similar quake would travel in a place like Southern California, where the earth’s crust is warmer, not as strong and where fault lines are wider.

Also has a little something to do with the depth of the epicenter, according to Dr. Carpenter. If it’s closer to the surface, it doesn’t have as far to travel upwards in order to create a little movement.

So the question remains, is Kentucky situated on fault lines, that could one day lead to a catastrophe?

“It's unlikely, and definitely it’s rare,” said Carpenter, who did point out evidence that leads geologists to believe much larger earthquakes did hit this region, hundreds of years ago.

“(Kentucky) is heavily faulted,” he said, “but most of those faults will likely never produce an earthquake. They just will not respond to the current stresses in the earth’s crust to generate a (sizeable) earthquake. There’s no reason to be concerned that something large would follow this earthquake.”

This earthquake on Monday was just enough to remind us that the term “terra firma” sounds nice, but the ground may not always be as solid as we think.