A spurious seismic reflection which occurs when energy is transmitted upwards from a subsurface shot and then reflected downwards from the surface of the ground or sea. A ghost wave train may interfere with other downward-moving waves, thus modifying their wave-form, and may add a reverberation tail. This type of ghost reflection is one kind of multiple event. A seismic event recorded from a reflector located outside the plane of the seismic section is called an ‘off-section ghost’ and may be a problem in an area where the three-dimensional subsurface topography is pronounced but only a two-dimensional seismic survey is being conducted.