Two and Three Dimensional Inversion of Magnetotelluric Data: Annual Report No. 2

摘要

We have developed an efficient iterative inversion method applicable to both 2 and 3-D magnetotelluric data. The method approximates horizontal derivative terms with their values calculated from the fields of the previous iteration. The equations at each horizontal coordinate then become uncoupled and 1-D with an added term containing the effects of the horizontal derivatives. At each iteration this allows separate 1-D inversions for the conductivity profile beneath each measurement site. Resultant profiles are interpolated to form a new multi-dimensional model for which the fields are calculated. Residuals to this new model are used in the next iteration. The method is very fast, as partial derivatives are calculated for 1-D problems only and computation time grows only linearly with the number of sites of data inverted. Preliminary tests with 2-D data show very promising results. Some practial problems remain in application of the algorithm to real 2-D data. We are requesting continued support to resolve these questions and to extend the method to 3-D. (ERA citation 13:025252)