Heard an explosion this morning, neighbor came by and said it was reported in next county over too but police and such couldn’t find any smoke or debris. I finally found a reference to it and it’s being called a “seismic-like” event? So they have no clue in other words…

https://www.volcanodiscovery.com/earthquakes/quake-info/6411543/quake-felt-Sep-17-2021-Near-Front-Royal-Virginia-USA.html