Locating sources of seismic energy by computing the semblance
along moveout trajectories requires knowledge of the velocity
Since our knowledge of the medium velocities is always imperfect,
there will be errors in the location of sources.
Using an incorrect average velocity results in a vertical shift of
the semblance maximum as compared with the actual source location.
The presence of random travel time fluctuations
causes a decrease in the maximum semblance value without
changing its location.