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Anyone familiar with the microtremor H/V method has prob- ably observed that even in presence of soft covers on stiff bedrocks it is very unlikely to see higher modes (cfr. also Figs. 8 and 10, [7]). Usually a strong impedance contrasts is marked by a single sharp H/V peak. Higher modes certainly exist but their amplitude is strongly attenuated due to the damping of soft soils. In case of stronger excitations (mid-large shear strains), like those induced by earthquakes, one expects that the anelastic damping is even larger. In no case do real transfer functions resemble the case of the black curve in Fig. 11B, obtained by using the laboratory
damping values.
The use of damping values measured in situ should be con- sidered in any realistic soil modeling. This also allows to avoid the costs of laboratory testing for a class of problems which are not controlled from the scale of the laboratory samples.