I thought it was an earthquake because the windows rattled, but the ground didn't shake. It turns out the whole county is mystified. Sound wave from the ocean? Military? Seismic activity? (I've heard earthquake booms before, but not like this.) Atmospheric re-entry?
It would be nice to see a boom-map like an earthquake did-you-feel-it shake map, so we could see if it's localized (with Miramar MCAS at the center?)