Authorities solve the mystery of town's odd noises, shaking From Jim Spellman, CNN March 23, 2012 -- Updated 1622 GMT (0022 HKT) The locations of the reported "booms" in Clintonville, Wisconsin. USGS now says it's the result of an earthquake "swarm" It measured one quake with a 1.5 magnitude Clintonville, Wisconsin (CNN) -- The mystery behind four days of unexplained shaking and odd sounds rattling Clintonville, Wisconsin, has been solved. The cause? A "swarm" of minor earthquakes amplified by the unique bedrock beneath the state of Wisconsin. The strange sounds -- variously described as rattling pipes, clanging metal, thunder or firecrackers -- have continued on and off since early Sunday night in just one part of the small town of 4,600, located about 180 miles northeast of Madison. They were loud enough Monday morning that a CNN journalist could hear them during a cell phone conversation with city administrator Lisa Kuss. Speaking to Clintonville residents Thursday night, Kuss said the U.S. Geological Survey has determined that "our community did in fact experience an earthquake that registered 1.5 on the earthquake magnitude scale." That minor quake was measured on Tuesday night by several mobile earthquake monitoring stations that were dispatched to the region, she said.. Based on all the data, the USGS believes the shaking and strange sounds are the result of "a swarm of several small earthquakes in a very short amount of time," Kuss said. While these small earthquakes normally don't cause such commotion, Kuss said the location of the shallow temblors helped amplify the shaking. "In other places in the United States, a 1.5 earthquake would not be felt," she said. But the type of rock that Wisconsin has transmits seismic energy very well. When the shaking began last Sunday, hundreds of residents began calling 911. Kerry Danley said she hear noises around midnight that sounded like a paintball gun. "It was just pop-pop-pop," she said. So I woke up -- just jumped out of bed actually -- ran downstairs, looked outside, nothing. Since Sunday, the shaking has happened nearly every night, quieting down during the day. Absent of any explanations, residents were left to their own devices to come up with explanations. Others suggested huge earthworms or sewer cats. Some Clintonville residents were even holding "shake" parties at night, waiting for the rumbling. As city officials ruled out electrical explosions, gas leaks and sewer collapses, they started consulting geological experts around the country. Based on the data from eight seismic monitoring stations, Kuss said the USGS finally determined on Thursday that earthquakes were to blame. While the cause of the shaking has been solved, it's still not clear if the rattling in Clintonville is over, Kuss said. "There is no way to say for certain whether our area will ever again experience an earthquake," she said. But it still very likely, although not guaranteed, that any future earthquakes that we experience would again be on the low end of the earthquake magnitude scale.