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Earthquakes the cause of Wisconsin town's annoying booms?

Clintonville City Administrator Lisa Kuss explains that recent mysterious booms that shook the small Wisconsin town may have been the result of a series of small, shallow earthquakes.

CLINTONVILLE, Wis. -- Did a minor earthquake cause the booming sounds plaguing an eastern Wisconsin city this week? Yes, the city administrator said at a news conference Thursday evening. Not so fast, a federal geophysicist said.

The U.S. Geological Survey did say that a 1.5 magnitude earthquake struck Tuesday just after midnight in Clintonville, a town of about 4,600 people about 40 miles west of Green Bay.

Geophysicist Paul Caruso told The Associated Press that loud booming noises have been known to accompany earthquakes. It's possible the mysterious sounds that town officials have been investigating are linked to the quake, he said.



Earthquakes can generate seismic energy that moves through rock at thousands of miles per hour, producing a sonic boom when the waves come to the earth's surface, Caruso said.

 

"To be honest, I'm skeptical that there'd be a sound report associated with such a small earthquake, but it's possible," he said.

Those reservations didn't stop Clintonville City Administrator Lisa Kuss from declaring "the mystery is solved" at a news conference Thursday evening.

She said USGS representatives described the event as a swarm of several small earthquakes in a very short time.

"In other places in the United States, a 1.5 earthquake would not be felt," she said. "But the type of rock Wisconsin has transmits seismic energy very well."

The U.S. Geological Survey says earthquakes with magnitude of 2.0 or less aren't commonly felt by people and are generally recorded only on local seismographs. Caruso said the Tuesday earthquake was discovered after people reported feeling something, and geologists pored through their data to determine that an earthquake did indeed strike.

Local residents have reported late-night disturbances since Sunday, including a shaking ground and loud booms that sound like thunder or fireworks. The booming continued Monday and Tuesday nights and into Wednesday morning, eventually prompting Jolene Van Beek to take her three sons to her father's home, 10 minutes away, so they could get some uninterrupted sleep.

 

Mysterious noises and ground vibrations are unnerving residents in Clintonville, Wis. WGBA-TV's Brian Miller reports.

"My husband thought it was cool, but I don't think so. This is not a joke," said Van Beek. "I don't know what it is, but I just want it to stop."

City officials investigated and ruled out a number of human-related explanations, such as construction, traffic, military exercises and underground work. They checked water, sewer and gas lines, contacted the military about any exercises in the area, reviewed permits for mining explosives and inspected a dam next to City Hall. They even tested methane levels at the landfill in case the gas was spontaneously exploding.

Clintonville resident Jordan Pfeiler, 21, said she doubted an earthquake caused the noises. She said the booms she experienced were in a series over the course of several hours and not continuous as she might have expected if they were caused by an earthquake.

Still, she said, "It's a little scary knowing Clintonville could even have earthquakes."

Steve Dutch, a geologist at the University of Wisconsin-Green Bay, said a 1.5 magnitude earthquake produces the energy equivalent of 100 pounds of explosives and could certainly produce loud sounds.

But he was reluctant to describe Tuesday's event as an earthquake, saying the term is generally used to refer to widespread stress in the earth's crust. What happened in Wisconsin could be near the surface, perhaps caused by groundwater movement or thermal expansion of underground pipes, he said.

Still, Dutch said it was possible that the event could produce a series of sounds over time.

Professor: Groundwater could be causing booms

Earlier, Kuss told The Green Bay Press Gazette that the city was spending $7,000 to hire an engineering firm in Waukesha, Wis., to install ground seismology monitors in four places around Clintonville late Thursday or early Friday.

Some residents are having fun with the mystery, which has drawn media attention from around the nation.

Jordan Pfeiler said people stayed up late on the first two nights to walk around listening for booms. They came up with outlandish theories to explain the noise - for example, that the White House was building an underground bunker in the area or that mole men had found a home there.

"And the aliens, of course, there's always the aliens," she said.

 The Associated Press contributed to this report.

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