Underground Cavity Detection Through Spectral Distortion of a GPR Signal

We present a novel method to detect underground cavities using cross-borehole ground-penetrating radar (GPR). We model the propagation of a GPR signal across a cavity and find that the spectrum of the signal will be distorted in a specific low-pass manner. Comparing the spectra of received signals with the predicted spectrum using a hypothesis-testing approach allows us to detect cavities with high probability. The proposed method is validated on both simulated and real measurements. Our approach generally remains effective even when conventional methods fail; our method can also be combined with conventional methods to more successfully distinguish between cavities and geologic clutter.