The harpazo(rapturo) happens to both dead and living. They are both caught up after the resurrection and they both get a new body. Just the same this happens as part of the resurrection. Notice in 1th 4:16 it says rise in the same context as Christ was resurrected. There is only one resurrection of the just.

Also notice in 1Co 15:54 that death is done away after we receive new bodies. How do people still die in the tribulation if death has been done away with?

1Th 4:16 For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first:

1Th 4:17 Then we which are alive [and] remain shall be caught up together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord.

1Co 15:54 So when this corruptible shall have put on incorruption, and this mortal shall have put on immortality, then shall be brought to pass the saying that is written, Death is swallowed up in victory.