3D Surface and Borehole Electromagnetic Imaging of

Finding good and stable reconstruction algorithms for 3D-Electromagnetic Induction Tomography is a big challenge nowadays due to the large scale and severe ill-posedness of the underlying inverse problem. The complete system of Maxwell's equations needs to be employed for modelling realistic situations, and data can usually only be collected at the surface of the earth and/or in some few boreholes. For the frequencies used (about 1KHz) , the  electromagnetic fields produced by the sources (usually large wire loops positioned above the ground) behave diffusive rather than wave-like in the earth.  These 'diffusive waves' have the advantage that they can penetrate quite deep into the earth, but due to this diffusive behavior the possible resolution in the reconstructions is very low, and the mathematical inverse problem is severly ill-posed. In addition, lower-dimensional (e.g. 2D-) approximations in most cases do not yield satisfactory results, such that the full 3D inverse problem needs to be solved.

In the project, we have developed a novel full-scale 3D inversion method for Electromagnetic Induction Tomography which is based on the single-step adjoint field technique. In addition, we have worked on the sensitivity analysis for imaging isotropic as well as anisotropic media with low-frequency electromagnetic fields.

You can download a first-year report on the EMSP Project:

Publications:

• O Dorn, H B Aguirre, J G Berryman and G C Papanicolaou: 'Sensitivity analysis of a nonlinear inversion method for 3D electromagnetic imaging in anisotropic media' (to appear in Inverse Problems) (pdf-file) (ps-file) 
• O Dorn, H B Aguirre, J G Berryman and G C Papanicolaou: 'A nonlinear inversion method for 3D electromagnetic imaging using adjoint fields', Inverse Problems 15, 1523-58  (pdf-file) (gzipped ps-file) 

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This page was created on 28 Aug 1998 and last changed on March 6, 2004..