Detection of Anthropogenic Change in a Lossy Mdeium by Orthogonal Dual Polarization GPR Measurement (40 MHz)

Orthogonal dual polarization GPR measurement was conducted for a purpose of detecting man-made structure buried in the subsurface. The target was two ∼2 m deep trenches which were made for geological investigation of a fault system 3 months prior to the GPR survey. The electrical conductivity of the subsurface medium was found to be ∼10 mS/m. The GPR survey was conducted at a frequency of 40 MHz. The survey area was defined as large as 9 m by 21 m. In the survey area were defined regular measurement grid points with the grid interval of 50 cm. Obtained data were processed to produce instantaneous power data, and are finally integrated to make 3D grid data set of each polarization measurement. Horizontal slice image of the difference of the two polarization images at a depth of ∼2 m show distinct image of the trench floors as well as the fault, which indicates that the orthogonal dual polarization measurement is effective in detection of man-made structure in a lossy medium.