So-called "mystery booms" that have puzzled residents in California's Gold Country appear to be coming from a U.S. military installation over 100 miles away in the Nevada desert.

The Hawthorne Army Depot routinely destroys obsolete munitions on weekdays between the hours of 11:00 a.m. and 2:00 p.m—the period of time when many of the nearly 2,300 members of the Facebook group "Mother Lode Mystery Booms" have reported hearing the blasts.

Glen White, a science instructor at Columbia College outside Sonora, said the sound coming from Hawthorne appears to carry especially well in the summer months.

"I can't explain all the physics involved, but the atmosphere is bouncing in response to the energy and it's reflecting and bouncing (the sound) back down," White said. "The really odd part is people fairly close to the source of the energy, the explosions, aren't hearing it. The sound goes over them."

White began researching the source of the mystery booms last summer at about the same time as, coincidentally, a team of scientists from Southern Methodist University were granted permission to place a monitoring station at Columbia College as part of a larger project to detect nuclear explosions.

White said the SMU team wanted to calibrate four sensor stations, including the one at the college, using the known source of daily explosions in Hawthorne.

The blasts heard in the Mother Lode were charted by the sensors and timing and triangulation identified Hawthorne as the source, White said.

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