[DangeloInspections]

As others have already posted, these are the relief cuts made in hopes that by putting a cut in the concrete that makes a specific area where the concrete is weaker, thus increasing the chance that the concrete will pick this "seam" to crack. Most of the time the concrete will crack at it's weakest place, which would be where the relief cut is. One should have relief cuts for every 100 sq ft approximately.

This does not always work out this way, and concrete could crack anywhere.

Some folks will caulk this crack, especially near where it meets the garage door to minimize chance of pest intrusion. You can easily do this just under the door without doing all of the relief cut if all you care about is bugs getting in this crack.

If you do caulk this "seam" I would be leery of using 100% silicone, as if you down the road want to paint the floor or apply epoxy it will not adhere well to silicone. I suggest applying a more expensive two part epoxy resin product making sure it is flush with the floor. Then if you do paint or epoxy coat later you will not be able to even tell where the relief cuts are.

Understand that most folks never do this. There is no harm of leaving them as is. You can blow out or vacuum these cuts every so often to keep them clean.

I am assuming that you were exaggerating about the width. As previous posters have stated if that relief cut IS really that wide, you may have more serious issues that will need attention.

Hope that helps...Frank D.