Topic: the earth/Earth trembled?

I have a scene with multiple explosions, where the ground shook. Should I write that as the earth trembled or the Earth trembled? I assume the former since the whole planet doesn't tremble.

Re: the earth/Earth trembled?

You would use 'earth' in this sentence. It's similar to when and why you would capitalise titles like: 'Dad' and 'dad', 'Mum' and 'mum'.

If 'Earth' is used as a proper noun, then it is capitalized. If used as a common noun, then the word 'earth' is lowercased.