Identification of different modes of Rayleigh waves is essential in surface-wave surveys. Multi-mode Rayleigh waves can provide higher accuracy of the near-surface structure than the fundamental mode alone. However, some modes or frequencies of Rayleigh waves may be absent in the vertical-component seismic data. To complement the dispersion information, a method based on complex-vector seismic data is proposed. We construct the complex vector by setting the radial component and vertical component as the real part and imaginary part, respectively. Then, high-resolution linear Radon transform is used to obtain the multi-mode Rayleigh-wave dispersion image of the complex-vector seismic data. Based on different dispersion characteristics of the radial and vertical components, the dispersion images of the complex-vector seismic data show better performance against interferences and mode misidentification. Synthetic and field examples demonstrate advantages of the complex-vector method over the traditional vertical-component method in spectral bands and dispersion curve mode identification. Therefore, a more robust and accurate near-surface S-wave velocity structure can be expected compared to the traditional vertical-component Rayleigh-wave method.

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