Development of new quantitative interpretation techniques for applied geophysics.

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The goal of geophysics is to understand, and perhaps predict, the dynamic processes that move and shape the Earth beneath our feet, and to "look" into the Earth to see these processes in action, or their consequences. The process of "looking" generally involves the construction of a model that resembles, to the best of our knowledge and abilities, the true subsurface of the Earth. The model construction procedure involves updating automatically the parameters of a prospective model such that synthetic geophysical survey data computed for the model match the data that were actually acquired in geophysical surveys. This procedure is referred to as inversion. Inversion routines comprise two main components: a computational procedure for calculating synthetic data for a given Earth model, and an algorithm for successively updating the parameters of the model. The proposed research determines to (i) improve the mathematics used by computer programs to synthesize geophysical survey data for realistically complex Earth models, and (ii) improve the algorithms used to invert geophysical data. Recent advances have produced what is effectively the first generation of these programs for fully three-dimensional models of the Earth. However, the mathematical representations these programs use for the arrangements of rock types in the subsurface are basic, being neither flexible enough to cope with the complicated structures that occur in nature, nor precise enough to handle the dramatic changes between adjacent rock types that can exist for certain important features such as ore deposits. This research programme will investigate the use of more sophisticated and refined representations of the subsurface to overcome these problems. The result will be computer programs that can provide more detailed and more reliable models, or "images", of the subsurface. The advancements that will be made will be applicable to most areas of geophysics. However, the main context considered for the proposed research will be mineral exploration.