Airborne Em Inversion On Vertically Unstructured Model Grids

An efficient accurate algorithm has been implemented for the modelling of airborne, land, and marine controlled source electromagnetic data, providing 2D and 3D depth inversions of frequency and time domain data. This is achieved by decoupling the inversion grid from the modelling grid used in the finite difference simulation of the fields. The model grid consists of columns of rectangular prisms that can be arbitrarily discretised in the vertical direction: This helps to better define the topography and other interfaces without densely discretising the upper part of the resistivity model. The material averaging scheme used to map the model onto the forward simulation meshes on the fly was modified to increase modelling accuracy near topography. Furthermore, by setting the horizontal smoothing appropriately, the general geological setting of the survey area can be taken into account during the inversion.