Resonance versus Shape of Sedimentary Basins


 Sediment-filled basins are of interest both in exploration geophysics and in earthquake seismology in assessing their potential to amplify ground shaking. By means of numerical models, we present a number of dimensionless ratios between the main resonance frequencies that can be measured on the top of the basins and their geometry and mechanical properties, under the hypothesis of rigid bedrock. These resonance frequency ratios depend largely on the aspect ratio of the basins, whereas the mechanical properties of the sediments (specifically, the Poisson’s coefficient) do not substantially affect the horizontal resonance frequency ratios. We discuss whether the modal frequencies measured on real basins can be used to extract information about the basins themselves and whether the theoretical expected modal sequence can be used to design experimental surveys aimed at assessing the dynamic behavior of basins.