Statistics of semblance

Stacking velocities are often used in the processing of seismic data by applying normal moveout (NMO) corrections for a fixed velocity or velocity function (“stacking” velocity), then computing semblance for the set of corrected traces. A large value of semblance is taken to imply the presence of a signal associated with the corresponding stacking velocity. The question arises as to what is a “large” value of semblance. The theory developed here allows one to attach quantitative levels of statistical significance to the value of semblance.