CALDWELL, Kan. (AP) -- A magnitude 3.8 earthquake hit south-central Kansas on Monday, rattling windows and doors, but causing no reported damage or injuries.
The U.S. Geological Survey initially reported the earthquake that hit about 9 a.m. to be a magnitude 4.2 but later revised it to magnitude 3.8.
The epicenter of the earthquake was about 11 miles northwest of Caldwell, a town of about 1,000 residents near the Oklahoma border. The earthquake had a depth of 3.1 miles, the USGS said.
"We've got reports of it being felt at intensity level three, which means rattling windows, possibly some books falling off shelves, that sort of thing," said Paul Caruso, a geophysicist with the USGS National Earthquake Center in Golden, Colo.
It had been unusual for earthquakes to be reported in Kansas until this year, Caruso said. Since 2010, there have been 15 earthquakes within a 100 mile radius of Caldwell, which includes into Oklahoma, he said. All but one of those earthquakes occurred in 2013, he said.
A recent study by the U.S. Geological Survey said that from 1975 to 2008, there were only a handful of earthquakes at magnitude-3.0 or greater each year in Oklahoma. But the average grew to around 40 annual earthquakes from 2009 to 2013.
Scientists are not certain what's causing the increased seismic activity, but one theory says it could be related to wastewater from oil and gas drilling that's often discarded by injecting it deep into underground wells. South-central Kansas also has seen increased oil drilling the last couple of years.
The Sumner County Sheriff's Office said there were no immediate reports of damage or injuries.
Lincoln Crampton, who has a woodworking business outside Caldwell, said he initially thought Monday's quake was a truck running off a nearby road. He said it lasted about six seconds.
"I didn't know what was going on. We usually don't get those. ... My mind doesn't go to that," Crampton said. "The house shook for a while. There were some pretty good rattles in the house."