“The louder ones sounded like somebody was throwing snowballs at the house,” Kammes said.
Neighbors heard noises too, and several contacted police.
“It wasn’t the regular noise you hear when your house is creaking, blowing in the wind or ice is breaking,” Kammes said.
The light flashes reported by some people are believed to come from electrical changes that occur when the freezing compresses rocks.
Robert Herrmann of the Saint Louis University Earthquake Center said frost quakes are far different from real earthquakes. Tremors typically occur a mile or two underground. Frost quakes are near the surface and do not show up on seismographs.
“People nearby will probably notice them a lot because they are shallow, but because they do not penetrate deep within the earth, the magnitude will not be large,” Herrmann said. “But the process is the same. There is something that is causing rock to move, and as the rock moves, it generates sound waves and the ground motion.”
AccuWeather meteorologist Alex Sosnowski said frost quakes are most common in the northern Plains.
“It has to get suddenly colder,” Sosnowski said. “If you have a mild winter, you’re probably not going to have a lot of this going on.”
Experts say damage is rare but homeowners who experience a frost quake should check for foundation cracks and watch for damage to water and natural gas lines.
Damage is not common, but it happens. In Waupun, Wis., a frost quake last month created a 100-foot crack in a driveway. Homeowner Dennis Olssen told authorities the boom was so loud he thought it was an explosive until he learned that neighbors experienced the same thing.
Kammes said the noise on that otherwise quiet night was so alarming that her husband went outside to make sure no one had damaged the home.
“When we found out what it was,” she said, “it was actually a relief.”