According to this article, a 1.7 magnitude Earthquake caused a Big Boom in Philadelphia, PA.
1.7 Magnitude quake?
Thanks for this thread. I saw a news story about the mysterious boom but missed the follow up today.
I find a nearby earthquake disturbing. I’m also concerned that last week a tornado touched down a few miles from my apartment. This is Philly! We are not supposed to have tornadoes or earthquakes.
Immigants! I knew it was them! Even when it was the bears, I knew it was them 
Yeah, really.
That’s right, Philadelphians, when I was recently visiting your city I took the liberty of leaving some disaster bombs for you.
So if you don’t want to have a volcano erupting in the middle of Independence Hall, you will pay me the sum of … ONE MILLION DOLLARS!
1.7? Andy Reid has had farts register higher than that. We had a 3.6 down here last year, and got laughed at.
Bahhh…
This was bound to happen sooner or later…big city…there is always somebody somewhere “turning Japanese” at any given moment…you guys just had enough at the same time for it to register…