As you can see from the latest images of asteroid 2005 YU55, it doesn't look much like a space ship, as claimed by certain internet personalities. Also, I'll remind you that the asteroid will not hit Earth or the Moon.
But will it cause earthquakes (or change the Moons orbit)? That's another persistent rumour flying around the bloggosphere. Lets look at it this way, the asteroid has a diameter of 0.4 km, the Earth.s diameter is 12742 km, something like 30,000 times that of YU55. Now, tidal force is proportional to the mass of the objects and falls off as the cube of the distance, and YU55 is 0.85 Lunar Distances away so we would expect that the tidal force of YU55 on Earth will be negligible.
But what about a control, we know of another massive object one Lunar Distance away, that's the Moon itself. The Moon diameter is 3476 Km, nearly 10,000 times that of YU55. Does the Moon cause Earthquakes? No.
If the Moon doesn't cause a significant number of earthquakes, then a lump of rock nearly 10,000 times smaller isn't going to either (and if YU55 hit the Moon, the effect on the Moons orbit will be negligible too, it would be like ramming a Hot Wheels car into an Aircraft Carrier).