Bucks County PA has been experiencing mysterious booms since April, and to hear the media talk about it, this is an entirely local phenomenon with no real history. The sounds are typically localized rather than spreading over a wide area as would the sonic boom of a passing jet that was flying faster than the speed of sound. The booms are also accompanied by ground shudders, but they are not powerful enough to be recorded as earthquakes. One of the few ways a boom like this could be produced is if something was moving straight down at supersonic speed. Another possibility is that the booms are caused by something underground, but the fact that they migrate suggests that the sound is generated by overhead activity.
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The phenomenon of mysterious booms is continuing around the world, with the sound of unexplained explosions being reported from locales as diverse as Michigan, Lapland, St Ives, Swansea and Yorkshire.

Booms reported by residents of six counties in Alabama have been investigated by police, NASA, and the Birmingham Alabama National Weather Service, with the latter tweeting on November 14:

"Re: loud boom heard: we do not see anything indicating large fire/smoke on radar or satellite; nothing on USGS indicating an earthquake. We don’t have an answer, and can only hypothesize with you. 1) sonic boom from aircraft; 2) meteorite w/ current Leonid shower?"
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 It’s not from fracking. And it’s not registering on seismographs as earthquake activity. Yet, it rattled livestock, people and their homes over a wide swatch of central Oklahoma (Norman, Edmond, and Shawnee) last Thursday and Friday, January 8th and 9th. Through this is not the first time it’s happened, nobody knows what or why it is.

 
Here’s a story on the subject by Linda Moulton Howe, investigative journalist/reporter and documentary writer-director-editor.read more