"[This is] likely the explanation for loud noises heard in the northern part of the Salt Lake valley," Jozens said. "Aircraft noises, explosions and other military operations conducted on the UTTR can sometimes be heard on the east side of the Great Salt Lake. If weather conditions are just right, sound will carry, ricochet and even be amplified and travels many miles."
Earlier Wednesday, HAFB officials had ruled out fighter jets stationed in Utah as the cause, saying that none of those aircraft were flying at the time of the booms. Jozens said officials had to go back and check the UTTR schedule to confirm that the Barksdale jets were training and were the likely cause of the noise as their ordnance hit the ground.
The booms reportedly were heard and felt across the Wasatch Range from Weber County south through Salt Lake and Utah counties.
Before the Air Force admission, the source of the booms became a matter of speculation. The University of Utah Seismograph Stations ruled out an earthquake, but confirmed that their ultra-low frequency sound monitoring equipment had picked up the noise.
"It was atmospheric, above ground. Typically, that can be a plane breaking the sound barrier, an explosion or a storm," said seismologist Katherine Whidden.
There also had been no notice of any artillery or munitions training activities Tuesday night at the Utah National Guard's Camp Williams site in southwestern Salt Lake County. There also were no unannounced activities at the base to explain the booms, assured UNG Lt. Col. Hank McIntire.
"We weren't blowing anything up last night. No artillery was being fired, no munitions being blown up. It wasn't us," he said.
There also had been some speculation that the booms which triggered dozens of calls to local law enforcement dispatchers may have been related to booster rocket testing at ATK's Box Elder County facilities. Not so, said Trina Patterson, a spokeswoman for the aerospace company, who confirmed there had been no such testing at the site Tuesday night.
Likewise, Rio Tinto spokesman Kyle Bennett said there had been no night-time blasting activity at the Kennecott open pit copper mine, also in southwestern Salt Lake County.
The National Weather Service, meantime, dismissed storm activity as the cause; but lead forecaster Pete Wilensky said that the winter air inversion plaguing northern Utah's valleys may have bounced the boom sounds over a distance from some unspecified source.