"Thunder" is a symbol of the effect of the Power of God's creative physical and spiritual-moral Laws.  

 "Thunder" is God's Laws in their power and force of Truth, exposing man's sin, punishing him by the consequences of his iniquities committed, "shaking" him, changing his worldview and way of life.

 "Thunder" symbolizes the spiritual Power of the Truth of God's Word, proclaimed by the righteous, which "shakes" and exposes the false religious, ideological, political foundations of sinful living nations.