Impact of gradational electrical properties on GPR detection of interfaces

Detecting subsurface media interfaces is a common practice for most geophysical methods and more specifically ground penetrating radar (GPR). In the majority of GPR applications, the boundaries of these interfaces are assumed to be sharp. Quite often interfaces are gradational and are difficult to detect and consequently map. Previous work has mainly focused on more simplistic one-dimensional modelling. In this paper, we employ three-dimensional (3D) finite-difference time-domain (FDTD) numerical modelling to address this problem. We examine the impact of a gradational zone in electrical properties (conductivity and/or relative permittivity) between underlying layers on GPR signals. The thickness of this transition zone and the GPR operating frequency have a significant impact on the GPR reflected wavelet amplitude and character.