The use of the inversion of single-station Rayleigh wave ellipticity curve in routine site investigation: numerical inversion and case-studies

Non-invasive single-station ambient vibration recordings have become very common nowadays for microzonation studies. Usually, these records are processed using Nakamura’s method to determine the horizontal-to-vertical spectral ratio (H/V) curve, but the Rayleigh waves’ ellipticity curve can also be determined and inverted alone or combined with data acquired using other surface wave methods. Since single-station ambient vibration-based analyses are a very cost-effective technique, this paper studies the reliability of the shallow ground structure that results from the ellipticity curve inversion, with prior knowledge on the ground profile characteristics, as is common in urban areas. The inversion of the ellipticity curve of a large set of shear wave velocity profiles (Vs-profiles) was simulated numerically to characterize the uncertainty. Three normally dispersive case studies in Lisbon County were used to evaluate the technique. RayDec was used to obtain experimental ellipticity curves inverting the right flank and the complete curve. It is shown that the Rayleigh wave ellipticity curve inversion can be a valuable and cost-effective preliminary site investigation technique, adopting a constrained inversion (based on some prior knowledge), to support the preliminary design stage of geotechnical works).