The town of Clintonville, Wisconsin has been rattled by mysterious underground booms for at least three nights and officials announced today that seismometers would be placed around the city to try and find the epicenter of the noise, according to the Green Bay Press Gazette.
City administrator Lisa Kuss said the city would be spending $7,000 to hire engineering firm Ruekert & Mielke to investigate the noise further. If the firm is able to find the epicenter, they can then try to pinpoint the depth of the noise and the origin. Kuss told the audience of townspeople, "It's possible we'll never have a definitive answer."
The sounds, described as rumbles of thunder, sonic booms or fireworks, started on Sunday night and have continued, aggravating residents, according to the Associated Press. The city ruled out immediate theories such as earthquakes, mining, truck traffic and water pressure, leaving no explanation for the booming, shaking noises.
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There have been no reports of damage or injury, though frustration is mounting in the city, said the AP.
The city set up audio and video recorders overnight but captured nothing, according to USA Today. The city has also ruled out sanitary and storm water system problems, methane and propane gas levels, military activity and construction.
A geologist at the University of Wisconsin-Green Bay, Steve Dutch, told the AP the ground beneath the city is solid granite and there are no known earthquake faults in the area. Dutch theorized that if water filling the cracks in the granite had fallen below the normal level of the water table, it could cause the rocks to settle, making the loud booms.
Some of the residents still have humorous theories on the booms, including the construction of an underground bunker, mole men and aliens.
Here is a video report from the AP: