A rare earthquake rattled Nebraska. What made it an 'unusual one'?

Nebraska experienced a rare, magnitude 4.2 earthquake Sunday afternoon that set floors shaking and pots banging but didn't appear to cause any damage.

"Our feet were just jiggling and bouncing around," said Kim Harig, who was working at the Webster County Community Hospital in Red Cloud, Nebraska, on Sunday afternoon when the quake hit.

"I said, 'Do you feel that?' and my colleagues all felt it. I said, 'It must be an earthquake.'"

It was, in fact, a 4.2 earthquake whose epicenter was about 15 miles to the northeast of Red Cloud, just above the Kansas border in the southeastern part of the state. The US Geological Survey put the exact location at 6.2 miles north-northeast of Guide Rock, Nebraska.

USGS instruments measuring the quake tagged it as being a Level IV, which is light intensity, defined as "felt by many; sensation like heavy body striking building. Dishes rattle."

Harig said she'd never felt an earthquake before, even after living in California for a time. "It was fascinating, I went online to find out what had happened."

Her colleague Marcia Schriner was in the hospital kitchen when the temblor struck at 1:31 pm local time.

"The floor was shaking and I thought, 'Is somebody on the roof?'" she said, adding that the quake felt like it lasted about ten seconds.

"I have a pot hanger in the kitchen and they were all banging together," Schriner said. "Nothing fell in the kitchen, there are no big cracks in the ground."

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Earthquakes in Nebraska

While not common, earthquakes do occur in Nebraska, said US Geological Survey geophysicist Paul Caruso.

"We have earthquakes in every state, though this was an unusual one," he said.

Nebraska isn't on a major tectonic plate boundary as the West Coast is but it can still have earthquakes. "They're a result of rocks breaking and moving underground. When they move, they release energy and we feel that energy as an earthquake," Caruso said.

Detectors showed that the quake was centered about four and a half miles below the Earth's surface.

Caruso said USGS's Did You Feel It? website, which gathers information from people who have felt earthquakes, had gotten close to a dozen postings, but no damage reports. He encouraged those who felt it to report on their site.

"It really helps us to zero in on the effects," Caruso said.

Nebraska's strongest quake was in 1877

The strongest earthquake in Nebraska history took place on November 15, 1877, according to the Nebraska Emergency Management Agency.

While there were no accurate measurements of magnitude available at the time, from reports of damage to buildings, the quake’s two shocks were estimated to have an intensity of VII, classified as Very Strong.

That quake hit in two jolts 45 minutes apart. According to the Nebraska Emergency Management Agency, "buildings rocked at Lincoln and walls were damaged at Columbus. The shock was strongly felt at Omaha. Cracked walls were reported at Sioux City, Iowa."

Eighty-seven years later, a large area spanning western Nebraska, South Dakota, and border areas of Montana and Wyoming was jolted by a magnitude 5.1 earthquake on March 28, 1964, causing cracks in some roads and some chimneys to fall.