You can modify the motion blur applied to your composition on individual layers, so that each layer appears to be moving at a different speed than other layers—see Adding Motion Blur and Depth of Field to a Scene.

To modify the motion blur on a layer:

1. Select a layer from the Layer Editor.
2. Enter a value in the Time Dilation field. A higher value speeds up the blur effect for the layer; a lower value slows it down.