Combining genetic and linearized algorithms for a two-step joint inversion of Rayleigh wave dispersion andH/Vspectral ratio curves

Abstract

S U M M A R YThe joint inversion of Rayleigh wave dispersion and H/V curves from environmental noise measurements allows the retrieval of S-wave velocity profiles for the shallow subsoil. For this purpose, genetic and linearized algorithm have been combined in a two-step inversion procedure, that allows the principal drawbacks typical of the application of each algorithm separately to be overcome. In the first step, a genetic algorithm procedure is used to constrain the subvolume of the parameter space where the absolute minimum of the misfit function is located. In the second step, a linearized inversion algorithm, having as an initial guess the minimum misfit model deduced from the first step, is applied to force the inversion towards the optimal solution. To evaluate the feasibility and effectiveness of this approach, seismic noise recordings at a test site in the Po river valley (North Italy) have been analysed. Here, detailed geophysical and geological information is available along with earthquake recordings, which allow a well constrained definition of both the local shear wave profile and transfer function. Comparisons between theoretical and experimental S-wave velocity profiles and, above all, between the theoretical and experimental site response functions shows that this combination of inversion procedures can very efficiently to manage the extreme non-linearity of the problem.

Alternative interpretations of horizontal to vertical spectral ratios of ambient vibrations: new insights from theoretical modeling

“…The second one concerns the physical interpretation and modeling of the ambient vibrations wave field. This is a fundamental pre-requisite to establish a link between observations and subsoil structure and thus using ambient vibrations to infer dynamical properties of the subsoil Tokimatsu 2004, 2005;Parolai et al 2005b;Picozzi and Albarello 2007;Herak 2008). On this topic, a strong debate has developed in the last years.…”

“…HVSR have been extensively studied to detect the fundamental resonance frequency of a sedimentary cover (see, e.g., Haghshenas et al 2008 and references therein) and retrieve information on the subsoil seismic layering Tokimatsu 2004, 2005;Parolai et al 2005b;Picozzi and Albarello 2007;Herak 2008). These last inversion procedures rely on two major competing hypotheses.…”

Assessment of seismic hazard in the Erzincan (Turkey) region: construction of local velocity models and evaluation of potential ground motions

“…HVSR methods can be used in inversion schemes in combination with SPAC data (e.g., Tokimatsu, 2004, 2005;Picozzi and Albarello, 2007;Hayashi et al, 2011;Ikeda et al, 2013). In this study, a simpler approach is used whereby in addition to the quantitative fitting of SPAC curves, peak frequencies of observed and modeled HVSR curves are matched to constrain depth of deep interfaces.…”

Love wave contribution to the ambient vibration H/V amplitude peak observed with array measurements

“…Several studies have since applied this kind of joint inversion (e.g. Arai and Tokimatsu, 2005;Nagashima and Maeda, 2005;Parolai et al, 2005;Garcia-Jerez et al, 2007;Picozzi and Albarello, 2007;Arai and Tokimatsu, 2008;D'Amico et al, 2008). Others use additional data, for example from borehole or array measurements, to fix either the sediment thickness (e.g.…”