Cause of Mysterious Booms in Northwestern Wisconsin Still Unknown

Saturday night, Sept. 9, around 9:30 p.m., residents reported hearing mysterious booms across the region.

Posting to online social media, people said they heard the noise in Chetek, Cameron, Barron, Weyerhaeuser, Trego and even Hudson and Cushing. Some said it sounded like distant thunder, though there was not a cloud in the sky Saturday night.

Theories sprang forth. Was it a tiny, imperceptible earthquake, a shooting star, a jet breaking the sound barrier or just your crazy neighbors shooting some high-powered fireworks?

There was a 9 p.m. fireworks display in Barron for Fall Fest, and Barron County dispatch logs do report other fireworks in Rice Lake. But it is not likely that fireworks in Rice Lake would be heard in Chetek. Perhaps, coincidentally, there were others closer.

But what if the booms weren’t fireworks. Could it have been something else?

Did it come from above?

This reporter, camping on the Flambeau River, did see a meteor streak east to west that night and large meteors have been known to cause quite a commotion.

On Feb. 6, a very bright meteor, called a “fireball,” streaked across the sky over Wisconsin and Lake Michigan, illuminating the night sky and shaking the ground with a sonic boom. It was heard and seen by residents and captured on security cameras in Wisconsin and Illinois.

But astronomy and physics professor Nathan Miller, at the University of Wisconsin-Eau Claire, is skeptical it was a meteor, even if Sept. 9 was the peak of the Epsilon Perseids meteor shower. Those shooting stars move at 40 miles per second, but they would have been silent to those on the ground and falling at a rate of less than one per hour.

“I would be really surprised if the Epsilon Perseids had enough large objects in a batch to cause a series of booms,” Miller said Monday, Sept. 11.

Mike Hankey, with the American Meteor Society, said they have received no meteor reports from the region either.

Perhaps the noise was caused by a jet breaking the sound barrier?

The Wisconsin Air National Guard does periodic supersonic training flights, as they did May 1-12 over central Wisconsin counties around Volk Field.

However, those flights were during the day and previously announced by the Wisconsin Department of Military Affairs.

No such announcements were made for Sept. 9 and Capt. Joe Trovato with the DMA said the booms were not related to any Wisconsin National Guard operations.

“I’ve asked around, and as far as I’ve been able to tell, we didn’t have any unusual operations or aircraft in that area,” Trovato said.

Did it come from below?

Another natural phenomenon could be tiny earthquakes, less than 2.3 on the Richter magnitude scale-too weak to be felt-called “microquakes.”

Published news reports said booms heard in Clintonville in March 2012 were thought to be very small (i.e. 1.5 magnitude scale or less) earthquakes.

Mitchell Withers, with the U.S. Geological Survey, the federal agency that studies geological events, is a bit skeptical of that explanation for the Clintonville booms, but does say that microquakes do occur.

“This [Clintonville] earthquake does tell us that there may be more tiny earthquakes in Wisconsin than we know about because of sparse station spacing,” Withers said. The closest seismograph station to Chetek is a ways away-56 miles-near Marine on St. Croix, Minn., but it has shown no activity on Sept. 9, nor for all of this month, Withers said.

A recent news blog based in Washburn County speculated that microquakes were being caused by recent large corona mass ejections from the sun-plasma from the sun shot outwards into space-causing low frequency (too low to hear) “acoustic-gravity waves” in the earth’s upper atmosphere, which caused “explosive fracturing” of the bedrock, resulting in the booms people heard. Much of the reasoning comes from clickbait conspiracy websites citing shaky science.

It is true the sun did have its largest corona mass ejection in 10 years on Wednesday, Sept. 6. Once it hit the earth a day later, there was some interference to satellites and some electrical and communication grids. Experts predicted auroras as far south as Iowa and Illinois. But all of that was estimated to end by late Friday, Sept. 8, local time.

Also, the USGS says there is no correlation between them; solar events don’t cause the earth to move.

“You are correct to be entirely skeptical of blogs connecting the solar flares with ‘explosive fracturing.’ BS detectors on high alert,” Withers wrote via email.

Still, he said, it is possible for compression waves from earthquakes to transfer into the air where we hear them. Those quakes have to be near the surface.

“The sound then would depend on the size of the earthquake and would probably be a bit like the crackle and pop on an old transistor radio, though only one pop per quake,” Withers said. But he remained skeptical.

“I don’t have a good explanation for the noises people are hearing, but I don’t think its earthquakes,” he noted.

So, the booms heard across the region don’t have an easy explanation, but many people say they did hear them. And it appears they haven’t harmed anyone or caused damage to structures or the land, so there is no cause for concern.

Maybe someday, science will discover the cause of the sounds, but for now they remain a curious mystery.

Carl Cooley
The Chetek Alert