'It sounded like a bomb going off': Loud boom heard Friday in Lake County remains a mystery

There is no question many northern Lake County residents either heard or felt something Friday afternoon. But what it was remains a mystery.

At about 3:30 p.m., emergency dispatch centers began getting reports of what sounded like a large explosion. Some social media posters said their homes shook. Many described what they experienced on a website called Volcano Discovery.

The situation passed in an instant but generated a lot of curiosity among residents in several communities. Had a home or business exploded? Was it an earthquake? A sonic boom? No one is certain.

"It sounded like a bomb going off. At the same time, my chair shook," said Antioch resident Bob Blameuser. "I expected to hear sirens."

About the same time, Lake County sheriff's deputy Michael Nudi was outside his vehicle taking a report at Route 41 and Stearns School Road near Wadsworth when he heard "one big boom."

"All of a sudden, we heard what I thought was an explosion," he said. "I pegged it several miles north of my location."

Other deputies also heard a noise and began checking their areas. But there was no evidence anything had blown up in Lake County. And authorities in southern Wisconsin said Monday there were no explosions or related reports Friday afternoon.

"We were never able to pinpoint it," Nudi said Monday. "I'd love to figure it out. It's just a big mystery at this point."

Unconfirmed reports of an earthquake began circulating shortly after. Nudi said he had experienced two minor earthquakes in the past, but Friday's event was not like that and he didn't feel the ground shake.

"You can feel the ground moving. It's almost like you're dizzy," he said of earthquakes.

Blameuser felt something and isn't sure what to think. At the time, he called to his son upstairs, thinking a piece of heavy furniture had fallen.

"It sounded like somebody dropped a bowling ball next to me," he said.

Don Blakeman, a geophysicist and analyst with the U.S. Geological Survey's Earthquake Information Center, said nothing registered Friday in northern Lake County.

"I don't see anything I could remotely call an earthquake at that time," he said. "We haven't located anything."

"That doesn't mean we couldn't have missed a small event," he added.

Sonic booms are often mistaken for earthquakes, according to Blakeman. So are mining blasts.

According to the National Aeronautics and Space Administration, a sonic boom is a thunder-like noise a person on the ground hears when an aircraft flies overhead faster than the speed of sound, about 750 mph. The boom creates a shock wave, like a boat creates a wake in the water.

Whether that may have been the case Friday in Lake County remains unknown.

Blakeman said small earthquakes can happen "just about anywhere," but northern Illinois isn't seismically active.

"I would love to know what it was," Nudi said. "It's driving me nuts."