Investigating Basin Resonances with 3D Physics-Based Ground Motion simulations

Sedimentary basins play a critical role in ground motion amplification, owing to their complex seismic wave propagation behaviors, which include 2D/3D resonance phenomena and basin edge effects. These characteristics make sedimentary basins key targets for ground motion studies.

A reliable proxy of the seismic response of sedimentary layers is their resonance frequency. This is often assessed through experimental measurements using Horizontal-to-Vertical (H/V) spectral ratio technique, applied to ambient seismic vibrations or earthquake records.

Since resonance frequencies depend on the geometry and mechanical properties of the resonating layer, they can be used as a benchmark for evaluating the accuracy of ground motion models, as simulated ground motion is expected to reproduce amplification at these frequencies.

In this study, we compare basin resonances derived from real and simulated waveforms in two different sedimentary settings in Italy: the narrow Alpine Bolzano basin and the wide intermountain Fucino basin in the Central Apennines. Using stratigraphic data from the literature, we construct 3D models of the basins and perform 3D seismic wave propagation simulations with a spectral-element code. We use both real and synthetic sources to simulate ground motion at the surface and calculate H/V and SSR ratios of the simulated waveforms to be compared with empirical ratios derived from earthquakes and ambient noise.

We analyze the similarities and discrepancies between real and simulated resonances, enabling an evaluation of the goodness of the velocity model used in the simulations. Furthermore, the seismic response of the basins is explored, including an investigation of 1D and 2D dynamic behaviors.