Wisconsin Noises: Solved
Swarm of earthquakes rocked Clintonville
It was difficult to tell where the noises were coming from. Sometimes they sounded like "rattling pipes," other times like "distant thunder." Sometimes they were accompanied by a rattling or shaking of the earth, although it was difficult to tell which came first. Were the noises making the earth tremble, or vice versa?
The U.S. Geological Survey has finally solved the superficial mystery: the noises were due to a "swarm" of shallow surface earthquakes. These earthquakes caused a variety of noises, depending on what they were shaking at the time. And obviously they would account for localized trembling of the ground, as well.
