Weird loud booms in northern California

Mysterious booms are rattling citizens of El Dorado County, California. Quarry owners require government permission to use explosives. The local Naval Air Station denies any supersonic flights over the area. Some have suggested that perhaps wineries are employing propane canons to scare away birds. From CBS Sacramento:

According to USGS, there aren’t enough seismic stations to pinpoint the exact location. Meanwhile, some say the booms have been around so long and happen so often they barely notice them anymore. Still, others want to solve the mystery.

“I would like to know what it is, yeah. And I’d like to know when it’s going to stop too,” said (Pleasant Valley resident Peter) O’Grady.

"Source Of Loud Boom In Foothills A Mystery" (via The Anomalist)