Impact of spatial sampling and antenna polarization on 3D GPR fracture detection

Three-dimensional Ground Penetrating Radar (3D GPR) surveys are needed to reconstruct subsurface fracture networks in terms of strike, dip and interconnectivity. This particular GPR study conducted in the Madonna della Mazza quarry (Italy) compares the impact of a dense acquisition grid versus antenna polarization on the characterization of subvertical fractures. 3D GPR data were acquired using a 250 MHz antenna over a 20 × 20 m area with a grid bin size of 5 × 5 cm. According to the quarter-wavelength criterion, profile spacing of 5 cm allows to properly sample also the high-frequency content of the signal spectrum. The results demonstrate that, rather than repeated surveys with different antenna orientation but larger profile spacing, a single survey with a regular and highly sampled grid is a preferred approach for high-resolution characterization of three-dimensional fracture networks.