That wasn’t thunder.

Residents in northern Jefferson County were surprised by the news that a 3.1-magnitude earthquake hit the area during the weekend.

“It woke us up in the middle of the night,” said preschool teacher Tari Stutz, who lives about a mile and a half outside Nortonville. “It just sounded like one of those dull roar kind of thunders that shakes the whole house.”

According to the U.S. Geological Survey, the quake happened at 3:15 a.m. Saturday about five miles north of Nortonville and was felt by residents of Atchison and Nortonville.

Rex Buchanan, associate director of the Kansas Geological Survey, said the earthquake was right on the border between the kind that can be felt and the kind that can’t.

“We’re not talking about a major earthquake by California standards,” he said. “To the best of my knowledge, there’s not a named fault that’s responsible for it. : We don’t show mapped faults over there, but that doesn’t mean they don’t exist.”

Earthquakes are the result of shifts deep below the earth’s surface. In Kansas, the most notable fault line is the Humboldt fault, which stretches from El Dorado to Riley County and is associated with a buried granite mountain range.

According to the U.S. Geological Survey, the biggest earthquake in the state’s history was April 24, 1867, in Riley County. The 5.1-magnitude quake was strong enough to knock stones off a church in Lawrence.

Buchanan said that given the lack of any significant earthquakes reported in the Nortonville area in the past, it’s not likely that this weekend’s quake is a precursor for a bigger one.

“I would worry a lot more about a car wreck on the way to work tomorrow,” he said.