2.5D Inversion Algorithm of Frequency-Domain Airborne Electromagnetics with Topography

Abstract

We presented a 2.5D inversion algorithm with topography for frequency-domain airborne electromagnetic data. The forward modeling is based on edge finite element method and uses the irregular hexahedron to adapt the topography. The electric and magnetic fields are split into primary (background) and secondary (scattered) field to eliminate the source singularity. For the multisources of frequency-domain airborne electromagnetic method, we use the large-scale sparse matrix parallel shared memory direct solver PARDISO to solve the linear system of equations efficiently. The inversion algorithm is based on Gauss-Newton method, which has the efficient convergence rate. The Jacobian matrix is calculated by “adjoint forward modelling” efficiently. The synthetic inversion examples indicated that our proposed method is correct and effective. Furthermore, ignoring the topography effect can lead to incorrect results and interpretations.

Stratigraphic Identification with Airborne Electromagnetic Methods at the Hanford Site, Washington

“…2D or 3D geological complexity exists (e.g., see Cox et al, 2010;Ellis, 1998;Raiche et al, 2001;Wilson et al, 2006). Several 2D and 3D modeling and inversion analyses have also been developed (e.g., by Cox et al, 2010;Heagy et al, 2017;Noh et al, 2018;Sasaki, 2001;Xi and Li, 2016;Yang et al, 2014); however, their acceptance has been limited because the number of observations used in the inversion was restricted due to computational constraints, or because the inversion codes were not publicly available.…”