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@INPROCEEDINGS{vonHebel:139363,
      author       = {von Hebel, Christian and Mester, Achim and Huisman, Johan
                      Alexander and Bikowski, Jutta and Rudolph, Sebastian and
                      Vereecken, Harry and van der Kruk, Jan},
      title        = {{T}owards {L}arge {S}cale {M}ulti-{L}ayer-{C}onductivity
                      {I}nversion of {Q}uantitative {E}lectromagnetic {I}nduction
                      {D}ata},
      reportid     = {FZJ-2013-05359},
      year         = {2013},
      abstract     = {Electromagnetic induction (EMI) systems enable high spatial
                      resolution measurements within short times. Multi-offset EMI
                      devices sense different depths and allow in principle a
                      better vertical characterization of the subsurface, but lack
                      in quantitative measurements due to static shifts that occur
                      due to the influence of cables and/or operator. To calibrate
                      the recorded apparent electrical conductivities (ECa) a
                      linear regression between predicted ECa, obtained from a
                      Maxwell-based exact forward model using inverted electrical
                      resistivity tomography (ERT) data as input, and measured ECa
                      is performed. Recently, a two-layer inversion was
                      introduced, using a combined one dimensional global-local
                      search (GLS). The global-search optimizes along a regular
                      grid using an approximate model. The subsequent local-search
                      uses a Simplex minimization and an exact forward model. This
                      approach uses no smoothing or damping to assure sharp layer
                      boundaries. Here, we extended the GLS to three-layers. Thus
                      the parameters increased from three to five enlarging the
                      solution space and increasing the difficulty to find the
                      global minimum. The GLS was implemented without and with
                      lateral constraint which compared the current optimizations
                      with the parameters obtained prior to that position. Large
                      deviations called a new global and local search before
                      inverting the next position. Moreover, a
                      shuffled-complex-evolution (SCE) optimization was
                      implemented that inverts each position separately using the
                      exact forward model. Experimental EMI and ERT transect data
                      were acquired at the Scheyern research farm of
                      Helmholtz-Zentrum-München. Performance and reliability of
                      GLS and SCE were tested by running the optimization from
                      start-to-end and from end-to-start of the profile. The GLS
                      inversion results without lateral constraint showed a strong
                      direction dependency indicating that the solution space
                      consisted of too many local minima that trapped the
                      inversion. The constraint stabilized the inversion, but the
                      results still remained direction dependent. The SCE
                      inversion results were direction independent indicating that
                      the global minimum was found. Smoothly changing layer
                      properties were obtained without large lateral jumps.
                      Comparison with ERT inversion results showed similar lateral
                      and vertical conductivity changes. The three-layer
                      multi-configuration EMI inversion based on the SCE
                      optimization is a powerful and widely applicable tool to
                      image subsurface conductivity variations.},
      month         = {Mar},
      date          = {2013-03-04},
      organization  = {73. Jahrestagung der Deutschen
                       Geophysikalischen Gesellschaft, Leipzig
                       (Germany), 4 Mar 2013 - 8 Mar 2013},
      subtyp        = {Other},
      cin          = {IBG-3 / ZEA-2},
      cid          = {I:(DE-Juel1)IBG-3-20101118 / I:(DE-Juel1)ZEA-2-20090406},
      pnm          = {246 - Modelling and Monitoring Terrestrial Systems: Methods
                      and Technologies (POF2-246)},
      pid          = {G:(DE-HGF)POF2-246},
      typ          = {PUB:(DE-HGF)6},
      url          = {https://juser.fz-juelich.de/record/139363},
}