Abstract
The shear wave velocity profile is of primary interest for geological characterization of soil sites and elucidation of near-surface structures. Multichannel Analysis of Surface Waves (MASW) is a seismic exploration method for determination of near-surface shear wave velocity profiles by analyzing Rayleigh wave propagation over a wide range of wavelengths. The inverse problem faced during the application of MASW involves finding one or more layered soil models whose theoretical dispersion curves match the observed dispersion characteristics. A set of open-source MATLAB-based tools for acquiring and analyzing MASW field data, MASWaves, has been under development in recent years. In this paper, a new tool, using an efficient Monte Carlo search technique, is introduced to conduct the inversion analysis in order to provide the shear wave velocity profile. The performance and applicability of the inversion scheme is demonstrated with synthetic datasets and field data acquired at a well-characterized geotechnical research site.
Highlights
Shear wave velocity (VS ) is a fundamental parameter in geological engineering due to its relations to the small-strain shear stiffness (Gmax )
The inverse problem faced in Multichannel Analysis of Surface Waves (MASW) analysis is by nature ill-posed, two-layer parametrization, all the theoretical dispersion curves shown in Figure 20a visually match the non-linear, mix-determined and non-unique
For applications of MASW where the sole objective is to assess the average shear wave velocity of the site (e.g., velocity in the top-most 30 m (VS30) ), the results presented here suggest that the layering parameterization plays a minor role, provided that the inversion is not severely under-parameterized and converges to a model whose theoretical dispersion curve is consistent with the experimental data
Summary
Shear wave velocity (VS ) is a fundamental parameter in geological engineering due to its relations to the small-strain shear stiffness (Gmax ). Various techniques exist for evaluation of in-situ VS -profiles [1,2,3], including both invasive techniques and active- and passive-source surface wave analysis methods. Proposed classification schemes have further suggested the use of the average shear wave velocity over the top-most z meters (VSZ ), alongside other geotechnical parameters, for seismic zonation purposes (e.g., [12,13,14,15]). Surface wave analysis has been proposed as a monitoring tool, where repeated measurements are carried out to assess the quality and depth of soil improvement or compaction [20,21]. The shear wave velocity of soil materials has further been related to numerous other geotechnical parameters through empirical correlations (e.g., [4,22,23,24,25])
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