Yes, these are earthquakes but in these verses they are not.
- 1 Chronicles 16:30: "He hath fixed the earth firm, immovable."
- Psalm 93:1: "The world also is stablished, that it cannot be moved."
- Psalm 96:10: "He hath fixed the earth firm, immovable..."
- Psalm 104:5: "Who laid the foundations of the earth, that it should not be removed for ever."
- Isaiah 45:18: "...who... fixed it fast
Immovable means that it cannot
be moved - i.e by something or someone else.
Not that it cannot move at all.
The earth can rotate on its own axis and move, in a circuit, around the sun - that's it. It cannot go anywhere else.
It is not going to wander around the night skies, so that we get too close to/too far away from the sun and get burnt up or freeze. It is not suddenly going to find that it has wandered off, got lost and is in danger of falling down a black hole. And no other force in the whole universe - angels, demons or whatever are going to pick the earth up and put it somewhere else or throw it around. No wind can blow it off course.
Why can't it? Because God has made it that way. God wants it to be where it is so that we - the people he created, lived and died for - can have life.
I don't know any technical details but someone has said that if this planet were a fraction closer to/further away from the sun, life could not be sustained. If the earth rotated a fraction faster we'd fall off. If any things that sustain life on our planet were different, we wouldn't be here.
(Someone else here may know the full details.)
That is amazing. And it is so because God, our Creator, wants it to be so. None of it is down to luck, chance or whatever; God made it that way. God decided, God created, God established.
The Bible doesn't spell any of this out or give scientific/astronomic details - because it is not a scientific textbook and that is not its purpose. But, I am sure, that is what the authors meant - this is God's wold and it cannot be altered or moved by anything else.