Controlled-source seismic interferometry is a method of obtaining a virtual shot gather from a collection of physical shot gathers. The set of traces corresponding to two common receiver gathers from many physical shots is used to synthesize a virtual shot located at one of the receivers and a receiver at the other. An estimate of the Green's function between these two receivers is obtained by first crosscorrelating corresponding pairs of traces from each of the shots and then stacking the resulting crosscorrelograms. We studied the structure of crosscorrelograms obtained from a VSP acquisition geometry using surface sources and downhole receivers. The model is purely acoustic and contains flat or dipping layers and/or point inclusions that act as diffractors. We propose a semblance analysis based on moveout curves for both point diffractors and flat or dipping layers, which can be used to improve the quality of redatumed traces either by rejecting certain events prior to stacking or by enhancing them.