present tense vs past tense

I just read a newspaper, then I saw a sentence which make me feel confused.

My question is why they used “move” and “collapse” instead of in past tense form since that they already used “saw”.

why they used “move” and “collapse” instead of in past tense form since that they already used “saw”.-- That is the reason exactly: ‘saw’ is the main finite verb, while ‘move’ and ‘collapse’ are infinitives (they function as verb complements) and they do not change whatever the tense of the main verb:

I saw the earth move.
I will see the earth move.
I have seen the earth move.
I had never seen the earth move.

This happens with several verbs of sensation (among others):

I felt the earth move under my feet.
I heard the bell ring.

etc.

Sir, I don’t get it what are you trying to say. Could you explain to me what criteria make some verbs as finite verb and other verbs as infinitives?

Each clause takes one finite verb only (except for compound verbs: ‘I ran and played all day’). Any verbs following the finite verb of the sentence (infinitive or participle) are non-finite. Start by reading more about these HERE and HERE.