Spectral-analysis-of-surface-waves (SASW) is a nondestructive test method for characterization of the variation with depth of the shear modulus of soils. One drawback in SASW is the need for an experienced user to conduct the inversion. Difficulty in SASW inversion arises from lack of constraint of the least squares minimization used on shear wave velocity parameters. For even simple profiles. The inversion algorithm can exhibit instability due to numerical sensitivity of the forward model calculations. The user must provide a reasonable starting profile; and then the parameters must be carefully followed and constrained to reach convergence. The inversion process was explored using a range of dispersion curves ranging from simple to complex layering systems. Three key principles were built into a new protocol to provide necessary constraints on the inversion algorithm. Dispersion data from many test sites have been inverted using the new protocol. Careful adherence to the protocol consistently produces shear wave velocity profiles indicative of site conditions. The protocol provides logic necessary for automation of the inversion process
