Revelation 8 & 9

1. What is God doing by giving these visions of judgement?
2. The visions do not seem to scare unbelievers into repentance; they actually seem to have the opposite effect (9:20-21). Who is the target audience for the warnings here?
3. Which people will be safe from the wrath of God?
4. How do we know who have been "sealed"?