How do we know that refers to this though?
Rev 16:17 The seventh angel poured out his bowl into the air, and a loud voice came out of the temple, from the throne, saying, "It is done!"
Rev 16:18 And there were flashes of lightning, rumblings, peals of thunder, and a great earthquake such as there had never been since man was on the earth, so great was that earthquake.
Rev 16:19 The great city was split into three parts, and the cities of the nations fell, and God remembered Babylon the great, to make her drain the cup of the wine of the fury of his wrath.
Rev 16:20 And every island fled away, and no mountains were to be found.
Rev 16:21 And great hailstones, about one hundred pounds each, fell from heaven on people; and they cursed God for the plague of the hail, because the plague was so severe.