ModelHVSR—A Matlab ® tool to model horizontal-to-vertical spectral ratio of ambient noise

Abstract

ModelHVSR is a user-friendly collection of Matlab ® routines performing a number of tasks related to analysis of microtremor data. Its distinguishing features include: • Computation of amplification spectra for horizontally stratified soil models, for vertically incident P- and S-waves. Q-values may be frequency dependent. For constant- Q models dispersion of body-waves is taken into account; • Computation of theoretical horizontal-to-vertical spectral ratios (HVSR) for body-waves, using estimates of both horizontal and vertical amplification of soil; • Computation of average observed HVSR using standard procedures or Landweber-filtered spectra; • Computation of linear amplification factors (DAF) of the peak-ground acceleration for any soil model and target earthquake; • Inversion of the observed HVSR spectra by Monte Carlo perturbation of initial model parameters, to obtain the best-fitting family of models; • Computation of confidence regions for all inverted model parameters (including DAF). The program may be used during microzonation or similar studies, when one needs to either verify the existing geotechnical models by comparing theoretical HVSR to the observed one, or invert the observed ambient noise measurements to obtain the most-likely geotechnical models of the soil. It is also useful to conduct sensitivity analyses and to explore possible biases between model parameters.