Reproducing Experimental H/V Spectral Ratios of Ambient Vibrations: Empirical Testing of Current Numerical Models

Abstract Horizontal-to-vertical spectral ratios of ambient vibrations represent an important tool to provide information about the seismic configurations of subsoil. This requires the application of inversion procedures based on numerical models aiming at reproducing observations from hypothetical subsoil configurations. In the current literature, several models have been proposed on purpose, which, however, provide different outcomes when applied to the same configuration. To evaluate how and at what extent the proposed models can fit observations, experimental ambient vibration measurements have been collected at 116 sites in central Italy, in which reliable VS and VP profiles were available from standardized downhole measurements. The comparison between experimental curves and outcomes from all the alternative models proposed in the literature has been carried out. This comparison confirms some theoretical findings about the best-performing models but also reveals that a significant fit is obtained only in about 80% of cases. This suggests that all the considered models present important limitations, possibly related to the general assumption of a 1D subsoil configuration and suggests caution in considering outcomes of the current inversion procedures.