RT Journal Article SR Electronic(1) A1 Carcione, José M. A1 Gei, Davide A1 Botelho, Marco A.B. A1 Osella, Ana A1 de la Vega, MatiasYR 2006 T1 Fresnel reflection coefficients for GPR‐AVA analysis and detection of seawater and NAPL contaminants JF Near Surface Geophysics, VO 4 IS 4 SP 253 OP 263 DO https://doi.org/10.3997/1873-0604.2005049 PB European Association of Geoscientists & Engineers, SN 1873-0604, AB ABSTRACT We obtain the transverse electric (TE) and transverse magnetic (TM) Fresnel reflection coefficients for different interfaces in the subsoil: air/fresh‐water, air/seawater, fresh‐water/seawater, air/NAPL (non‐aqueous phase liquid), NAPL/water and water/NAPL. We consider a range of NAPL saturations, where the complementary fluid is water with 0.65 ppt (parts per thousand) of NaCl. The common feature is that the TM mode (parallel polarization) has a negative anomaly and the TE mode (perpendicular polarization) has a positive anomaly. For the cases studied in this work, pseudo‐Brewster angles appear beyond 40° for the air/NAPL and NAPL/water interfaces and at near offsets (below 40°) for the water/NAPL interface. Pseudo‐critical angles are present for the water/NAPL interface. Besides the reflection strength, the phase angle can be used to discriminate between low‐ and high‐conductivity NAPL, when the properties of the upper medium are known. A wavenumber–frequency domain method is used to compute the reflection coefficient and phase angle from synthetic radargrams. This method and the curves can be used to interpret the amplitude variations with angle (AVA) of reflection events in radargrams obtained with ground‐penetrating radar (GPR)., UL https://www.earthdoc.org/content/journals/10.3997/1873-0604.2005049