Automated Surface Wave Method: Field Testing

The spectral analysis of surface waves (SASW) method is a nondestructive in situ seismic testing method for determining shear wave velocity profiles of soil sites and stiffness profiles of pavement systems. The key steps involved are construction of an experimental dispersion curve from data collected in situ, and inversion of the dispersion curve to determine the stiffness profile. In this paper, an automated method for the construction of dispersion curves is discussed. Weighted least-squares best-fit solution is used to estimate the phase at each frequency with coherence as weighing function. By knowing the distance between the receivers and the phase at each frequency, phase velocity and wavelength associated with that frequency are calculated. These raw data are then combined using the least-absolute-valuebest-fit criterion to construct a dispersion curve. The inversion process for determination of stiffness profile from the dispersion curve is described in a companion paper.