Geophysical Inversion for Mineral Exploration

Tuesday, April 23, 2002 - 1:30pm - 2:30pm
Keller 3-180
Douglas Oldenburg (University of British Columbia)
Mineral deposits are characterized by a variety of physical properties. For each property, a surface geophysical survey is carried out and a first goal of the analysis is to find a 3D distribution that reproduces the data and provides a geologically interpretable image. The inverse problem is large, and ill-posed, and is typically solved as an unconstrained optimization problem. The critical elements are the specification of measures of misfit and model norm, and deciding upon the appropriate relative weighting of these parameters in the final optimization. Considerable effort is required to design appropriate measures and I will outline our approaches in this talk.

Solution of the inverse problem provides a first image from which questions can be posed pertaining to existence, or detail, of structure. Answering these questions often requires further inversions of the data. Unfortunately, the cost of carrying out a single inversion is high, and practicality dictates that we answer our questions by carrying out a limited number of subsequent inversions. I illustrate our progress in this area with examples, and put forth some avenues for future research.