At first, Schuyler resident Dave Svoboda thought a vacant house had exploded.
About 17 miles to the south, Rick Schneider said he had the sensation of being on a cruise ship as he walked down the hallway of his David City home.
A 3.3 magnitude earthquake struck northeast Nebraska on Thursday morning, the second to rattle the state in two months.
“The whole house shook,” Svoboda said. “The glasses in the cupboard shook; you could feel the floor shake. Just about everybody in town felt it.”
While the idea of a Nebraska earthquake surprises many, it doesn't surprise those who track quakes.
On Sept. 26, a 3.0 magnitude earthquake rumbled up from the ground near Oconto, Neb.
“That's not unusual at all,” said geophysicist Paul Caruso of the National Earthquake Information Center in Golden, Colo. “These little earthquakes happen all the time.”
Caruso pointed to a “swarm” of earthquakes occurring in Oklahoma. According to the Oklahoma Geological Survey, 200 quakes have been recorded there this year, nearly 60 of which could be felt.
Caruso said there's no reason to fear that these minor quakes indicate a major one is imminent.
According to the U.S. Geological Survey, Nebraska and western Iowa are generally in a low hazard area for a major quake.
Still, there's no doubt that Thursday's quake rattled people.
Butler County emergency dispatcher Mike Rogers said about 70 calls flooded in as people tried to figure out if an explosion had occurred and whether they were in any danger.
“People have never experienced anything like this in their lives,” he said. “Some were laughing — just silly, nervous laughing — and some were scared.”
The quake occurred at 7:02 a.m. and was centered about 6 miles south of Schuyler.
Caruso said people living within 25 to 30 miles of the epicenter reported feeling the quake, although someone as far away as Tekamah also reported it.
Sensing a minor quake 70 miles away is not unheard of, Caruso said. Rock east of the Rockies transmits seismic energy well because it's so old and solid.
Seismographs as far away as Wyoming, Oklahoma, Colorado and Arkansas detected Thursday's earthquake.
A quake like this in Nebraska probably is a response to a more significant shift in the Earth's surface much farther away, perhaps as far away as the Atlantic or Pacific Oceans, Caruso said.
“These stresses are spread throughout the continent and are expressed as small earthquakes,” he said.
No fault line has been mapped where Thursday's quake occurred, one reason people were caught off guard.
The length of a fault determines the severity of a quake, Caruso said, with longer faults creating stronger quakes. Some faults can be just a couple of inches long while others can run for hundreds of miles.
No damage or injuries were reported Thursday, and that doesn't surprise Caruso, either.
Typically, a quake has to reach 5.5 magnitude before structural damage occurs, he said.
Since 1867, at least seven moderate earthquakes have occurred in Nebraska, according to the USGS.
The strongest occurred in 1877. Its epicenter was southeast of Columbus, and it is believed to have been a magnitude 5.1, according to the USGS. The quake rocked buildings in Lincoln and cracked walls in Sioux City, Iowa.
Another magnitude 5.1 quake occurred in western Nebraska near Merriman. Other less damaging, moderate quakes have occurred in Dawes County in the Panhandle, and near Norfolk and Tecumseh in eastern Nebraska.
Nebraska probably has a number of unmapped faults, said Matt Joeckel, a geologist and professor at the University of Nebraska-Lincoln.
“Earthquakes are more common than the uninitiated might think,” he said.
What concerns Joeckel is a lack of research about Nebraska's geology, especially about the known faults in the Omaha and Lincoln areas.
“Every time this happens, it's both frustrating and exciting,” Joeckel said. “It's frustrating to a geologist because we know there are things going on below the surface that we can't see, but we might be able to with more sophisticated monitoring.
“It's exciting because you don't have to go all the way around the world to see geology at work. You can see it here in Nebraska. You can feel it.”
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402-444-1102, nancy.gaarder@owh.com
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