A series of mysterious booms and bangs that spooked locals in a US town this week may have been triggered by tiny earthquakes.
Police received more than 600 calls within three days from fretful residents reporting the sonic booms in the Wisconsin town of Clintonville.
Resident Al Miller said it "almost felt like a heavy duty thunderstorm".
But experts have now linked the booms to earthquakes.
"The mystery is solved," Clintonville city administrator Lisa Kuss said.
One quake early last Tuesday was recorded by the US Geological Survey (USGS) at 1.5-magnitude.
USGS geophysicist Paul Caruso said quakes that size typically go unnoticed, but the ancient and consolidated rock in Wisconsin caused the tremor to have a larger than normal effect.
As for the rest of the strange roars and bangs, they could also have been the result of miniscule earthquakes. Read More