I believe that wake turbulance can only be created by the wings of an aircraft that is flying, and has nothing to do with "jet blast." Thus a plane that takes off before the rotation point of the previously departing plane will avoid wake turbulance if it then stays above or away from the vortices that are created by the wingtips of the departing plane. Similarly, if one were to land beyond the touchdown point of the previous plane, while remaining above the glide path of the previously landing plane on approach, there would be no wake turbulance.