"It depends. Are gravity waves longitudinal or transversal? In other words, are they like sound waves where the oscillation parallels the direction of propagation, or are they like light waves where the electric field oscillates perpendicular to the direction of propagation?"
Great question. Sound is longitudinal because the medium is compressed by the energy from the sound source. Light is transversal because the electric and magnetic fields collapse as they propogate the photon.
As a wild guess, I'd say transversal. There's no medium to compress. Gravity is supposed to have quanta like light as well, (although I suppose it's far smaller, since gravity is a far weaker force).
I'd say we'll have a better idea after this satellite records gravity waves--if it does.