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@ARTICLE{Klotzsche:155660,
      author       = {Klotzsche, Anja and van der Kruk, Jan and Bradford, John
                      and Vereecken, Harry},
      title        = {{D}etection of spatially limited high-porosity layers using
                      crosshole {GPR} signal analysis and full-waveform inversion},
      journal      = {Water resources research},
      volume       = {50},
      number       = {8},
      issn         = {0043-1397},
      address      = {Washington, DC},
      publisher    = {AGU},
      reportid     = {FZJ-2014-04713},
      pages        = {6966–6985},
      year         = {2014},
      abstract     = {High-permittivity layers, related to high-porosity layers
                      or impermeable clay lenses, can act as low-velocity
                      electromagnetic waveguides. Electromagnetic wave phenomena
                      associated with these features are complicated, not well
                      known and not easy to interpret in borehole GPR data.
                      Recently, a novel amplitude analysis approach was developed
                      that is able to detect continuous low-velocity waveguides
                      and their boundaries between boreholes by using maximum and
                      minimum positions of the trace energy profiles in measured
                      GPR data. By analyzing waveguide models of different
                      thickness, dip, extent, permittivity, and conductivity
                      parameters, we extend the amplitude analysis to detect
                      spatially limited or terminated waveguides. Waveguides that
                      show high-amplitude elongated wave trains are most probably
                      caused by a change in porosity rather than a change in clay
                      content. In a crosshole GPR data set from the Boise
                      Hydrogeophysical Research Site, two terminated wave-guiding
                      structures were detected using the extended amplitude
                      analysis. Information gained from the amplitude analysis
                      improved the starting model for full-waveform inversion
                      which imaged the lateral extent and thickness of terminated
                      waveguides with high resolution. Synthetic data calculated
                      using the inverted permittivity and conductivity models show
                      similar amplitudes and phases, as observed in the measured
                      data, which indicates the reliability of the obtained
                      models. Neutron-Neutron logging data from three boreholes
                      confirm the changes in porosity and indicate that these
                      layers were high-porosity sand units within low-porosity,
                      poorly sorted sand, and gravel units.},
      cin          = {IBG-3},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {246 - Modelling and Monitoring Terrestrial Systems: Methods
                      and Technologies (POF2-246) / 255 - Terrestrial Systems:
                      From Observation to Prediction (POF3-255)},
      pid          = {G:(DE-HGF)POF2-246 / G:(DE-HGF)POF3-255},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000342632300041},
      doi          = {10.1002/2013WR015177},
      url          = {https://juser.fz-juelich.de/record/155660},
}