Although this is technically second-hand information - I've posted on the subject before with first-hand experience. In the western area of Arizona, we are experiencing regular, yet sporadic intervals of window-rattling, deeply low frequency "tones", rumbles and loud "booms". I use quotes with "booms" since these are not ordinary sonic booms or explosives that we are aware of.
After checking around, I've learned that there hasn't been a blasting permit issued within 100 miles of us in over a decade. There are ZERO seismic readings published that would indicate earthquake or tremor activity and I've reached out to our local newspaper to encourage them to investigate.
After reading my letter and contacting me with permission to edit and publish my letter to the Editor, the story never ended up getting printed. After numerous attempts to find out why and to connect with the Editor's assistant, no one will return my calls or answer my e-mails.
I have only been respectful and have not "overly bombarded" them for an answer, so I'm amazed that they flat-out refuse to acknowledge this subject.
The case file officially is at 10:05 pm AZ time, my contact experienced a sequence of 30 minutes long, 20 rumbles and several "booms" in the same fashion that we have been experiencing separately for over a year now.
These "booms" sound more like an impossible amount of weight being dropped and hitting the ground, as opposed to a quake, sonic boom or bomb test / mining explosion. There is a distinct "tone" about them as they occur which seems to drive the neighborhood dogs crazy. It "feels" like pressure on the eardrums and then slowly become audible and eventually turns into a rumble.
Neither of us have experienced a "huge, bright white (or green) light" with this audible and physical experience. But I've just recently read about others seeing unexplainable light phenomena with this sounds in southern AZ.
We really need investigators on this! Anyone willing to look into it, would have an incredibly high chance of experiencing this if they gave it a few nights.