On Friday, Twitter lit up with reports of a boom that was felt in James Island and West Ashley. (I felt it too, which is unusual since I am typically oblivious to such things.)

Whenever I get reports like this, the first place I go is to USGS’s earthquakes map. Typically, when the jolt is strong enough for us to feel and it was seismic, there’s going to be something here pretty quickly. On this day, there was nothing on USGS.

The other type of jolt we feel most often around here are sonic booms, which occur as the result of trailing shockwaves from supersonic aircraft. Since the Concorde has been retired, that leaves military aircraft conducting exercises as the prime source of said booms. And sometimes, we can use weather radar to see some byproducts of these exercises, called chaff. This was the case on Friday morning with a chaff release very near the time of the sonic boom, giving increased confidence in our inference of the source of the boom.

It’s worth noting that not every sonic boom will be accompanied by a chaff release. However, when the shaking and then the chaff release happen within a reasonable amount of time from each other, it lends quite a bit of confidence in the sonic boom being the source of the shaking rather than anything seismic. This method is not foolproof, though.