Fast approximate physics method for 3D time-domain electromagnetic modeling

ABSTRACT Full 3D modeling of time-domain electromagnetic data requires tremendous computational resources. Consequently, simplified physics models prevail in geophysics, relying on a much faster but approximate 1D forward model. A method was introduced that combines the accuracy of a 1D simplified physics model with the flexibility of coarse grids to reduce modeling errors, thereby avoiding full 3D accurate simulations. The method was applied to time-domain airborne electromagnetics (AEM) data, generating data with a modeling error often smaller than the standard measurement noise level. The modeling error depends on the specific subsurface model (electrical conductivity values and angle representing the deviation of the 1D assumption) and the specific (temporal) discretization. Computation time can be decreased by a factor of 27. This modeling strategy may serve as an alternative to surrogate models or statistical relations derived from large 3D data sets.