Kansas’ top geologist says timing is one of the main reasons why more people than usual felt Thursday morning’s 4.7 magnitude earthquake that was centered 13 kilometers southwest of Cherokee, Oklahoma. It occurred at 1:42 a.m.
Interim Director of the Kansas Geological Survey, Rex Buchanan said, “It’s pretty quiet that time of day, as opposed to the middle of the day, when there might be a lot of car traffic, or people have their washing machines or dishwashers running, that sort of thing.”
Overland Park resident Eric Frischer was asleep in his bed when he felt the tremors.
“It felt like something was jumping up and down on my bed and the bed was actually creaking,” Frischer said. “I woke up, thinking somebody was in my room. The bed was creaking, moving slightly, vibrating and shaking. I looked around and nobody was there, of course. I sat up for about 30 seconds and it stopped.”
Frischer suspected the shaking might have come from an earthquake after being in one several years ago, but was surprised to learn that one had actually hit the area.
This is one of the stronger quakes felt in Kansas of late. Buchanan cited a 4.9 magnitude quake last November in South-Central Kansas as the strongest he had seen in his years.
The strongest earthquake in Kansas history was a 5.1, recorded near Manhattan in 1867. That quake was in the Humboldt Fault Zone, which is the main area of threat in Kansas from naturally occurring earthquakes, according to Buchanan. He said, “In theory, folks have talked about the possibility of at most, a 5.5 or maybe even a 6.0 along there, although we’ve never seen that.”
Buchanan says there’s no way to tell if any individual quake may be caused by man-made activity, like hydraulic fracturing.
However, he says, “In general terms, where you’ve seen such a huge increase in seismicity, folks are pretty confident that’s it’s highly likely the result of induced seismicity.”
In March, Kansas began requiring oil and gas operators in Harper and Sumner counties to reduce their injection rates. The Kansas Corporation Commission has continued that requirement through March 2016, according to Buchanan.
Buchanan chairs Kansas’ Induced Seismicity State Task Force.