Abstract
Recent studies have illustrated that the Multichannel Analysis of Surface Waves (MASW) method is an effective geoacoustic parameter inversion tool. This particular tool employs the dispersion property of broadband Scholte-type surface wave signals, which propagate along the interface between the sea water and seafloor. It is of critical importance to establish the theoretical Scholte wave dispersion curve computation model. In this typical study, the stiffness matrix method is introduced to compute the phase speed of the Scholte wave in a layered ocean environment with an elastic bottom. By computing the phase velocity in environments with a typical complexly varying seabed, it is observed that the coupling phenomenon occurs among Scholte waves corresponding to the fundamental mode and the first higher-order mode for the model with a low shear-velocity layer. Afterwards, few differences are highlighted, which should be taken into consideration while applying the MASW method in the seabed. Finally, based on the ingeniously developed nonlinear Bayesian inversion theory, the seafloor shear wave velocity profile in the southern Yellow Sea of China is inverted by employing multi-order Scholte wave dispersion curves. These inversion results illustrate that the shear wave speed is below 700 m/s in the upper layers of bottom sediments. Due to the alternation of argillaceous layers and sandy layers in the experimental area, there are several low-shear-wave-velocity layers in the inversion profile.
Highlights
The Multichannel Analysis of Surface Waves (MASW) method was initially developed as an inversion method in order to map the near-surface of Earth’s structure, by recording and analyzing dispersion of Rayleightype surface waves
Contemporary studies have exhibited that the MASW method is an effective geoacoustic parameter inversion tool, which employs the dispersion curve of Scholte-type surface waves on the seafloor [1,2,3,4,5,6]
In the ensuing sections of the manuscript, we present the theoretical formulas of the stiffness matrix method and their root-searching schemes
Summary
The MASW method was initially developed as an inversion method in order to map the near-surface of Earth’s structure, by recording and analyzing dispersion of Rayleightype surface waves. In order to overcome the obstacle of a high frequency numerical value, varying attempts have been made in the literature [9,10,11] Another common method for computing the dispersion curve is the reflection and transmission matrix method, which was proposed by Kennett [12,13]. This particular mechanism may be regarded as a major factor to be considered in establishing acoustic propagation models as well as in predicting sonar performance [22] It is an efficient and convenient method to estimate the velocity gradient of the shearing wave in the seabed by inverting the dispersion curve of the seawater–seabed interface wave [6,23]. The stiffness matrix method is employed in this particular study to directly relate the forces at the layer interface to the displacements at the same position. The theoretical dispersion curve of the surface wave propagating in the layered system can be ascertained
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