IV-4 PRE-STACK DEPTH MIGRATION FOR TIME-TO- DEPTH CONVERSION – THE ULTIMATE TOOL? Introduction The use of seismic data for accurately predicting the depth of a geological horizon remains one of the most difficult and risky tasks in the geophysicist’s job. In this paper we assess the role of Pre-Stack Depth Migration (Pre-SDM) as a depth conversion technique and question whether Pre-SDM can provide us with not only a better focused image of the subsurface but an image that is closer to true depth. There are many ways that the geophysicist can transform seismic data recorded as a function of wave