> For the detectives in the crowd.

> What does this photo depict?

I have seen two things that create similar patterns:

Interference patterns between 2 layers of cloth. If 2 layers are laid on top of each other at slightly different angles they can create a texture of parallel lines. When this is sanded you can get a similar pattern.

or: Tension wrinkles in the cloth. If the cloth has been rolled of a long time with wrinkles, it can cause a texture of parallel lines, or if the roll has been dropped, it can introduce tension into the cloth which also create parallel lines. These lines show up when you start sanding.