Joint estimation of modal attenuation and velocity from multichannel surface wave data

Abstract

We evaluated a method for the simultaneous analysis of velocity and attenuation of multichannel surface wave data. It allowed us to estimate the phase velocity and attenuation curves using an array of receivers, possibly unevenly spaced, and a set of multiple shots at different locations. After reviewing the properties of surface waves in dissipative media, the estimation algorithm was evaluated. It was based on the estimation of the complex wavenumber of multiple normal modes. It can be considered as a highresolution subspace-based method able to deal with irregularly sampled multichannel-multishot data. The interference between multiple modes was considered without the need of a prior specific multimode Rayleigh spreading function, so that multiple modal attenuation curves can be extracted. The validity of the approach was tested using synthetic data, with small and large mode interference, as well as with multimode real data. The benefits and the robustness of the proposed method were particularly relevant with data with multiple modes. The possibility of considering multiple shot points into a receiver array allowed the increase of the modal resolution without increasing the receiver aperture, thus without compromising the lateral resolution. The estimation of the modal attenuation coefficient enabled the estimation of the subsurface material damping ratio, and the definition of a dissipative propagation model.

Seismic inversion of soil damping and stiffness using multichannel analysis of surface wave measurements in the marine environment

“…However, it is shown that a simultaneous coupled inversion of the shearmodulus and damping ratio can be more accurate (Rix et al 1998;Lai & Rix 2002), though this may depend on the methodology used. The concept of the quality factor, as defined by Carcione et al (1988), was further extended to the modal phase-damping ratio and used with an estimate of the complex wavenumber to determine the material-damping ratio (Misbah & Strobbia 2014). Numerical solvers are required to determine the complex root solutions of a damped theoretical soil model.…”

Spatial Laplace transform for complex wavenumber recovery and its application to the analysis of attenuation in acoustic systems

“…[9][10][11][12][13][14] However, such techniques typically only supply real wavenumber information (or their magnitudes) from twodimensional, discrete, spatiotemporal wave propagation information, such as may be obtained from scanned receiver measurements. Several methods have been proposed to characterize wave attenuation and extract complex wavenumber information; [15][16][17][18][19][20][21][22] however, each has restrictions, as: (i) they are usually based on measurements of wave amplitude decrease with respect to time, [15][16][17][18] (ii) they are iterative methods applied in space, like the modified Prony method, 19 (iii) the number of modes has to be known in advance or a unique mode has to be isolated, [15][16][17]20,21,23 (iv) the modes contributing significantly to the signal are presumed to not interact or overlap with one another, or (v) they must include a third dimension of information, such as would be the case in an experiment with a scanned emitter and a receiver. 21,22 In this work, a method presenting none of these restrictions is proposed and applied to the analysis of complex attenuation phenomena in the scanned spatiotemporal measurements of three acoustic systems.…”

Advanced surface-wave analysis for 3D ocean bottom cable data to detect localized heterogeneity in shallow geological formation of a CO2 storage site

“…Although less attention has been paid to attenuation of surface waves, some studies used attenuation coefficients of surface waves to estimate quality factors of S-waves (e.g., Xia et al, 2002;Lai et al, 2002;Misbah and Strobbia, 2014). In strongly heterogeneous media, however, estimation of the attenuation coefficients would be influenced by energy reflection at the interfaces (Foti, 2004;Bergamo and Socco, 2014).…”