Those are called rolling lines of the stock material seen on the copper planchets more on the 1970's/80's cents. These are the rolling lines on the metal that show up after the BU look disappears from the coins. They are only surface lines. They eventually wear off the coin on the higher locations first, then then the fields. Not to be confused with woody coins. They are only surface. On the woody coins the poor mixture affects the whole planchet all the way through. Even on worn coins if the woody look was there from day one, they will still show on worn examples.
These rolling lines can be seen even on the zinc cents as well. Even the striking doesn't remove them:
So when the BU goes away expect to see these slowly wear off these coins as well.
Mike Diamond mentioned these are like printing on to the coin. On the highest devices they do wear off. Eventually they will all go away as they are just surface lines. Circulation wear will remove them They are not like woody appearances. Woody is all through the planchet/coins material because of a poor mix of metal. These are just surface lines left by the rolling process of the stock metal.