Removing Some of the Mystery from the “Mystery Booms” in the Mother Lode Region Glen White, Geologist September 19, 2014

Background: Numerous people throughout the Mother Lode region have reported deep booming noises of unknown origin. Since the origins were not immediately evident, they have been referred to as “mystery booms”. A Facebook page was set up to help record observations from witnesses and to allow people to speculate on the source of the noises. Anecdotal information indicates that the booms have been heard for many years (some reporting up to 200 years), at all times of the day, and throughout the year. Information is available to help remove the mystery from some of the booms. Historical, anecdotal, and reports from outside the Mother Lode region are not addressed here. Only scientifically collected data are used in this paper to explain some (perhaps most) of the noises heard in this region. The term “brontides” has sometimes been used to refer to these booms. Brontides are simply defined as deep booming sounds, possibly of seismic origin. (http://www.merriam-webster.com/dictionary/brontide)

Summary of Observations: Numerous witnesses reported their observations on the Mother Lode Mystery Booms Facebook page. The predominant pattern of reports indicated that booms tended to occur on weekdays between the hours of 11:00 AM and 2:00 PM. Occasional booms were reported outside of those boundaries. Some booms were heard widely from Amador, Calaveras, and Tuolumne counties, some seemed much more localized, while some were heard in a patchwork of locations. Portions of Calaveras and Amador counties had more reports than Tuolumne County. Some booms were reported shortly after their observation, others were reported up to many hours later. Thus, the timing of individual observations cannot be accurately correlated with each other. The booms seem to follow a seasonal pattern. Most booms are reported during the summer months, with few booms reported the remainder of the year.

'Boom' sounds still a mystery in Copper

Many residents of Copper from Kiva to Circle XX have been contacting the Copper Gazette regarding the sonic boom and/or explosion sounds they hear and feel almost daily between 12-1 in the afternoon.

After contacting Tuolumne County regarding possible explosive permits and active mining operations, it was stated that there are currently no active mining operations in Tuolumne County. George Reed does hold a permit for blasting at their Tabletop location, yet a spokesperson for George Reed stated that no afternoon explosions were run at that facility, furthermore any explosions at the facility occurred at two to three weeks intervals and between 9 and 10 am.