On the use of the Norwegian Geotechnical Institute's prototype seabed-coupled shear wave vibrator for shallow soil characterization - II. Joint inversion of multimodal Love and Scholte surface waves

Socco, Laura; Boiero, Daniele; Maraschini, Margherita; Vanneste, Maarten; Madshus, C.; Westerdahl, H.; Duffaut, Kenneth; Skomedal, E.

doi:10.1111/j.1365-246x.2011.04961.x

Cited by 34 publications

(21 citation statements)

References 40 publications

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“…20,21 However, Love-waves are very seldom used in an underwater environment, 7,22,23 since in conventional underwater and seismic experiments sources are deployed in the water column and only Scholte-waves can be generated. In order to generate Love-waves shear-wave sources located on the sea bottom must be used.…”

Section: Introductionmentioning

confidence: 99%

Estimation of seabed shear-wave velocity profiles using shear-wave source data

Dong

Nguyen

Duffaut

2013

The Journal of the Acoustical Society of America

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This paper estimates seabed shear-wave velocity profiles and their uncertainties using interface-wave dispersion curves extracted from data generated by a shear-wave source. The shear-wave source generated a seismic signature over a frequency range between 2 and 60 Hz and was polarized in both in-line and cross-line orientations. Low-frequency Scholte- and Love-waves were recorded. Dispersion curves of the Scholte- and Love-waves for the fundamental mode and higher-order modes are extracted by three time-frequency analysis methods. Both the vertically and horizontally polarized shear-wave velocity profiles in the sediment are estimated by the Scholte- and Love-wave dispersion curves, respectively. A Bayesian approach is utilized for the inversion. Differential evolution, a global search algorithm is applied to estimate the most-probable shear-velocity models. Marginal posterior probability profiles are computed by Metropolis-Hastings sampling. The estimated vertically and horizontally polarized shear-wave velocity profiles fit well with the core and in situ measurements.

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Section: Introductionmentioning

confidence: 99%

Estimation of seabed shear-wave velocity profiles using shear-wave source data

Dong

Nguyen

Duffaut

2013

The Journal of the Acoustical Society of America

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“…Based on their field experiences, Eslick et al (2008) concluded that a minimum thickness of 1 m of low-velocity material in the near-surface layer is needed to record usable Love-wave data in the frequency range of interest (5-50 Hz). A multimodal joint Scholte and Love wave inversion using Monte Carlo algorithm was proposed to analyze ocean-bottom data and detected lateral variations of the layer interface depths (Socco et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Advantages of Using Multichannel Analysis of Love Waves (MALW) to Estimate Near-Surface Shear-Wave Velocity

et al. 2012

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As theory dictates, for a series of horizontal layers, a pure, plane, horizontally polarized shear (SH) wave refracts and reflects only SH waves and does not undergo wavetype conversion as do incident P or Sv waves. This is one reason the shallow SH-wave refraction method is popular. SH-wave refraction method usually works well defining nearsurface shear-wave velocities. Only first arrival information is used in the SH-wave refraction method. Most SH-wave data contain a strong component of Love-wave energy. Love waves are surface waves that are formed from the constructive interference of multiple reflections of SH waves in the shallow subsurface. Unlike Rayleigh waves, the dispersive nature of Love waves is independent of P-wave velocity. Love-wave phase velocities of a layered earth model are a function of frequency and three groups of earth properties: SH-wave velocity, density, and thickness of layers. In theory, a fewer parameters make the inversion of Love waves more stable and reduce the degree of nonuniqueness. Approximating SH-wave velocity using Love-wave inversion for near-surface applications may become more appealing than Rayleigh-wave inversion because it possesses the following three advantages. (1) Numerical modeling results suggest the independence of P-wave velocity makes Love-wave dispersion curves simpler than Rayleigh waves. A complication of ''Mode kissing'' is an undesired and frequently occurring phenomenon in Rayleigh-wave analysis that causes mode misidentification. This phenomenon is less common in dispersion images of Love-wave energy. (2) Real-world examples demonstrated that dispersion images of Love-wave energy have a higher signalto-noise ratio and more focus than those generated from Rayleigh waves. This advantage is related to the long geophone spreads commonly used for SH-wave refraction surveys, images of Love-wave energy from longer offsets are much cleaner and sharper than for closer offsets, which makes picking phase velocities of Love waves easier and more accurate. (3) Real-world examples demonstrated that inversion of Love-wave dispersion curves is less dependent on initial models and more stable than Rayleigh waves. This is due to Love-wave's independence of P-wave velocity, which results in fewer unknowns in the MALW method compared to inversion methods of Rayleigh waves. This characteristic not only makes Love-wave dispersion curves simpler but also reduces the degree of nonuniqueness leading to more stable inversion of Love-wave dispersion curves.

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“…The work on nonlinear inversion can be found in Ivansson et al (1994), Ohta et al (2008) and Dong & Dosso (2011). More recently Vanneste et al (2011) and Socco et al (2011) used a shear source deployed on the seafloor to generate both vertical and horizontal shear waves in the seafloor. This enabled to measure both Scholte and Love waves and to inverse S-wave speed profile jointly, thereby obtaining information on anisotropy in the subsurface.…”

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confidence: 99%