We use synthetic calculations to investigate the spectral ratio between horizontal and vertical components (H/V ratio), derived from noise simulation, in order to appreciate the reliability of the so-called Nakamura\u27s method for site effects applications. This ratio shows a peak whose position generally coincides with the fundamental resonance frequency. We show that this position is independent of the source function, whereas it is characteristic of the geological structure. We also compare these results with those obtained for vertical S waves and Rayleigh waves, in order to better understand the significance of this HIV peak. Finally, we show that the amplitude of the H/V ratio cannot be used directly to derive the amplification for body waves, as suggested by Nakamura (1989), since it is very sensitive to parameters such as the Poisson\u27s ratio and the source-receiver distance
