Estimation of phase and group velocities for multi-modal ground roll using the 'phase shift' and 'slant stack generalized S transform based' methods

Roohollah Askari, Robert J. Ferguson and Kristof DeMeersman

ABSTRACT

Phase and group velocities are two important factors to determine shear wave velocity in Multi-channel Analysis of Surface Wave (MASW) surveys. In this study, we present two different methods "the phase shift and the slant stack generalized S transform based" for the estimation of the phase and group velocities respectively. The phase shift method uses the idea of the slant stack in the Fourier domain to estimate the phase velocity. The slant stack generalized S transform based method uses the slant stack idea in the time-frequency domain based on the generalized S transform. These methods are robust to estimate the phase and group velocities where ground rolls are multi-modal. We anticipate that, through inversion of the phase and group velocities of multi-modal ground rolls, a better estimation of near surface shear wave velocity will be obtainable.

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