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Vertical seismic profiles (VSPs) gained wide acceptance in the United States in the late 1970s because they appeared to have potential as a powerful exploration and reservoir characterization tool. However, today—more than a decade later—VSP data are still shunned by interpreters because they are deemed difficult to use and/or they are too expensive to justify the small amount of additional information they provide. Many of the problems stem from the very nature of the data. A VSP is like a refraction profile in that there is no pseudo cross section of the earth and the apparent velocities of arrivals are analyzed to provide indirect interpretations of layer configurations and interface dips. As with a CDP gather in reflection profiling, the VSP is largely insensitive to layer dip. It is this relative insensitivity to structure that makes the NMO correction of a CDP gather tractable and the processing of VSP data quick and simple. These characteristics require that the survey objectives and the anticipate...