DISPERSION-CURVE IMAGING CONSIDERATIONS WHEN USING MULTICHANNEL ANALYSIS OF SURFACE WAVE (MASW) METHOD

The multichannel analysis of surface wave (MASW) method can be an efficient tool for mapping the near-surface shear-wave velocity (Vs). Data acquisition, dispersion-curve imaging and estimations, inversion, and 2D visualization are distinct MASW components. Dispersion-curves can be estimated on images that can be obtained by various transforms including converting seismic data from the time-space domain (i.e., t-x domain) into frequency–wave-number (i.e., f-k domain) by applying the Fourier transform to both time and space, Phase-velocity–frequency domain (e.g., Cf-f or f-v domain), slowness–frequency domain (i.e, p-f domain), phase-velocity–wavelength domain, etc. It has been our observation that while the mathematical link between such transforms is well known, the relationship between the corresponding images can be visually clarified for better comprehension. In this work we show the visual relationship between the f-k and the Cf-f domain images. We also demonstrate the visual effects of using fewer geophones (i.e., data along the space axis) with different spread sizes on the phase-velocity–frequency dispersion-curve imaging using surface-wave data with dominant single- and multi-mode surface-wave forms of expressions. These examples could help better understand and make more efficient use of the MASW data acquisition, analysis, and interpretation of final results.