Magnetic Interpretation By Scanning Multiple Models For Best Least Squares Fit
G. Hunter Ware, Hunter Andreas Ware · 9th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems · 1996
Magnetic interpretation is generally accomplished by comparing discrete anomalies in the residual field with theoretical profiles of reasonable models. Simplified ‘rules of thumb” based upon sets of model curves are also employed. Direct analytical inversion of field data is impractical due to non-uniqueness and computational difficulties. The problem is that even the simplest models may be adjusted in depth, horizontal position, and orientation. More complicated models may also be varied in two- or three-dimensional shape, and may involve multiple bodies. It is therefore very difficult to optimize model parameters and measure the degree of fit or agreement with field data. We have developed a procedure called MAGFIT for automatically comparing actual and model profiles, and calculating a best least squares fit. With our algorithm, it is possible to rapidly scan a simple set of models (such as dipoles) over many locations and orientations, and determine the best fit as a function of position (and/or other model variables). “Best fit” plots generally show closed contours around a best tit of 60% to 90%, identifying the likely locations of magnetic bodies.