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Multi-channel spectrum analysis of surface waves

Spectrum analysis of surface waves (SASW) is one of the most effective non-invasive methods for soil characterization. Surface waves travel in the medium along a free boundary and can be easily detected by using a transducer placed on the free surface of the boundary. Traditional methods of SASW are two-station methods that use the phase information at two receivers to determine phase velocity as a function of frequency. Multi-station methods have also been developed by using a two-dimensional Fourier transform approach, but these methods exhibit poor resolution. We propose a new method based on vector processing of data obtained from an array of tri-axial sensors to produce a high resolution, multi-modal spectrum of the surface waves. These different modes can be identified and reconstructed in time domain, and then inverted to obtain the shear velocity profile of the subsurface.