Testing the horizontal to vertical spectral ratio technique as a tool for utility detection

Abstract In this study, experiments were conducted to explore the potential of utilizing the horizontal-to-vertical spectral ratio HVSR technique for detecting subsurface utilities. The hypothesis behind the adoption of this technique is that the presence of utility may produce impedance contrast that will affect the shape of the HVSR curve. Synthetic modeling and experiments revealed that the effect would be an extra spectral peak at the high-frequency end of the curve. The tests also aim towards the detection of the depth to the utility. An empirical formula was used to determine the depth, using the frequency of the additional peak and the shear wave velocity obtained from the Multichannel Analysis of Surface waves MASW measurements. Single-station and multi-receiver recordings were conducted at some localities at the Universiti Sains Malaysia main campus at Penang Island, northwest peninsular Malaysia. Areas of known subsurface utilities and the utility map, as provided by the development department of the university, were utilized to validate the results. The results obtained confirm the validity of the hypothesis, and a comparison of the obtained depths and locations of the utility shows an acceptable agreement.