And there were voices, and thunders, and lightnings - Accompanying the voice that was heard from the throne. See the notes on Revelation 4:5; Revelation 11:19.
And there was a great earthquake, ... - See the notes on Revelation 6:12; Revelation 11:19. The meaning is, that a judgment followed as if the world were shaken by an earthquake, or which would be properly represented by that.
So mighty an earthquake, and so great - All this is intensive, and is designed to represent the severity of the judgment that would follow.