The reason behind the recent earthquakes in Nebraska

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LINCOLN, Neb. – Four earthquakes have shaken Nebraska already this week. Despite what people may think, earthquakes are not a new thing here in Nebraska. According to the United States Geological Survey (USGS), there have been 46 since 1975.

However, in less than 36 hours, there have been four in central Nebraska. They can happen in Lincoln and all over the state, but the big question is what's causing them?

Most people think of earthquakes as windows breaking, things falling off shelves, buildings falling apart, and sometimes large cracks in the ground. For people in Arnold and Callaway, Nebraska, though, the earthquakes they felt weren't as severe. But, they did wake some people up Tuesday morning.

"I wasn't awake yet, but it brought me right out," said an Arnold resident.

"I don't know what that was but it sure shook this house," another said.

"There was a couple this morning again and those woke me up," said yet another Arnold resident.

There were three earthquakes in the area before 11 a.m. The biggest was a 3.7 magnitude as the sun was coming up. Another earthquake was recorded in the same region on Monday.

"Any earthquake below a magnitude 5 doesn't usually cause much damage at all," said State Geologist Matt Joeckel.

Joeckel is also the director of the Conservation and Survey Division at UNL. He said they're most likely due to fault lines that run a few miles underneath the ground.

"But it's certainly not a fault that we could map at the surface because if you know anything about this area of Nebraska, you know that there aren't any rock-out crops and mostly when we map faults we map them in bedrock," said Joeckel.

Because of this, Joeckel said Nebraska is unique.

"Perhaps what the only thing that's disconcerting about this is, in effect, how little we know about the geologic structure underneath Nebraska," said Joeckel.

Over the last four decades, earthquakes have happened all over the state, but never anything greater than a 4.3 magnitude.

"Every time there's an earthquake, however weak it happens to be, it's one more data point on the map, and one more small piece of data that helps us understand the geology of Nebraska better," said Joeckel.

The USGS website lists the strongest earthquakes in Nebraska in 2002 and 1978.