This research is to develop an improved inversion technique for seismic velocity models such as those required in oil exploration and crustal studies. A problem with current techniques is that an initial guess must be made as to the velocity model; this is then adjusted until it fits the observations. However, the final result is often dependent on the initial guess. An inversion method termed simulated annealing, based on a model of cooling to crystallization, attempts to avoid having to make an initial estimate in order to come up with the best final model that fits the seismic data. A second technique is termed a genetic algorithm based on biological principles of natural selection and genetics. Both are global optimization methods. If successful, the techniques will have wide application in seismic oil exploration and crustal investigations.