“So this is like a digital pen that sits right here. And this piece of paper is drawn across and it covers that distance in a minute. And then at 15 minutes, it jumps back over and it starts again.”
USI Geology Professor Dr. Paul Doss is displaying a seismogram on his laptop.
“… you see black, red, blue, and green lines…”
It’s the moment seismic waves from the earthquake in Turkey and Syria — like a large bell being struck — reached the USI equipment on campus 15 minutes later. It’s visualized as a violent set of squiggles across the screen.
“The energy that was released from the earthquake in Turkey was essentially instantaneous,” Doss said. “Maybe it lasted a minute, but the energy that it released, bounced around in Evansville’s crust for about three hours or so.”
The USI equipment is in a vault eight feet underground, digitally recording seismic activity.
Doss said earthquakes are caused by stress, created by movements within the Earth's crust.
“An earthquake is a strain response to stress,” he said. “And stress would be movements within the Earth's crust. And that movement of two big blocks of rock releases energy. And that release of energy is transmitted through that rock of the Earth's crust in the form of seismic waves.”
This seismic activity was measured in amplitude, because of its up-and-down motion. It couldn’t be physically felt by anyone here. Doss said the last "felt" earthquakes in the area were in 2002, and 2008, which were capable of causing some light damage.
Tremors undetectable by humans are common, like a 3.1 magnitude quake in Missouri on Thursday.
An earthquake struck New Madrid Missouri in 1811. Based on journal entries and reports, it was estimated to be about an 8 in magnitude.
The recent Middle East earthquake measured a 7.8.
Doss says the Tri-state area is on a fault line, which means earthquakes are possible here.
“Earthquakes are not random by any stretch of the imagination,” he said. “Earthquakes are most common and frequent, along what we call plate tectonic boundaries.”
Doss says it’s unclear when another earthquake might happen again, the last being about 2005.
He says such tragic catastrophic events can have global impacts. “We are firmly plotted in in a time of globalization. And so what happens elsewhere around the world absolutely has the potential to impact our lives here.”
He referenced the 2011 Japan earthquake which impacted jobs at the local Toyota plant in Princeton.
The current count is 20,000 fatalities from the Turkey/Syria earthquake.
“So whether it impacts any one individual here in the tri state — it's almost irrelevant. In my opinion, it absolutely impacts everybody on the planet,” he said. “It's a tragic event to happen no matter where it (occurs).”