On the efficient acquisition and holistic analysis of Rayleigh waves: Technical aspects and two comparative case studies

摘要

The present study illustrates a series of technical aspects regarding the holistic acquisition and analysis of Rayleigh waves acquired by a single multi-component geophone.Compared with the common multi-channel and multi-offset active and passive methodologies, this approach requires simple and straightforward acquisition procedures and takes advantage of the joint analysis of the group-velocity spectra of both the vertical and radial components together with the Radial-to-Vertical Spectral Ratio (RVSR), i.e. the ratio between the amplitude spectra of the radial and vertical components.In this way we can fully describe the Rayleigh-wave propagation both in terms of velocities (group-velocity spectra) and relative amplitudes (RVSR) and jointly invert the data by means of a three-objective optimization scheme based on the Pareto optimality.Since the group-velocity spectra of the vertical and radial components are analyzed according to the Full Velocity Spectrum (FVS) approach, data inversion is performed without interpreting the velocity spectra in terms of dispersion curves.The results of the described methodology are assessed by considering two case studies and by comparing the retrieved shear-wave velocity profiles with the ones obtained through the analysis of the dispersion retrieved from standard active and passive multi-channel and multi-offset data also considering the Horizontal-to-Vertical Spectral Ratio (HVSR).Eventually, through a synthetic dataset, the effect of significant lateral variations is discussed with respect to the group-velocity spectra and the RVSR and RPM (Rayleigh-wave Particle Motion) curves.