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@ARTICLE{Looms:851247,
      author       = {Looms, Majken Caroline and Klotzsche, Anja and van der
                      Kruk, Jan and Larsen, Thomas Hauerberg and Edsen, Anders and
                      Tuxen, Nina and Hamburger, Nancy and Keskinen, Johanna and
                      Nielsen, Lars},
      title        = {{M}apping sand layers in clayey till using crosshole
                      ground-penetrating radar},
      journal      = {Geophysics},
      volume       = {83},
      number       = {1},
      issn         = {1942-2156},
      address      = {Tulsa, Okla.},
      publisher    = {SEG},
      reportid     = {FZJ-2018-04942},
      pages        = {A21 - A26},
      year         = {2018},
      abstract     = {Fluid transport through clayey tills governs the quantity
                      and quality of groundwater resources in the Northern
                      Hemisphere. This transport is often controlled by a 3D
                      network of macropores (biopores, fractures, and sand lenses)
                      within the clayey till. At present, a nondestructive
                      technique that can map and characterize the sand-lens
                      network does not exist, and full excavation or extensive
                      drilling is therefore the only solution. Acquisition and
                      modeling of crosshole ground-penetrating radar (GPR) may
                      provide the answer to this problem. We collected 1D and 2D
                      crosshole GPR data at a field site in Denmark from four 8 m
                      deep boreholes with horizontal distances varying between
                      2.64 and 5.05 m. We find that the depth, thickness, and tilt
                      of a coherent sand layer within the clayey till
                      (approximately 0.4–0.6 m thick), as well as the underlying
                      sand formation, can be mapped accurately using GPR data. We
                      efficiently identify the sand as a highly resistive section
                      with high electromagnetic (EM) wave velocities, whereas the
                      clayey till is conductive with lower EM wave velocities. We
                      find that the exact location of the sand occurrences is
                      better delineated by the increase in amplitude than the
                      increase in EM wave velocity. We believe that crosshole GPR
                      may contribute significantly to groundwater protection and
                      contaminant remediation initiatives.},
      cin          = {IBG-3},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {255 - Terrestrial Systems: From Observation to Prediction
                      (POF3-255)},
      pid          = {G:(DE-HGF)POF3-255},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000429311000050},
      doi          = {10.1190/geo2017-0297.1},
      url          = {https://juser.fz-juelich.de/record/851247},
}