Estimation of near-surface shear-wave velocity by inversion of Rayleigh waves

The shear-wave (S-wave) velocity of near-surface materials (soil, rocks, pa vement) and its effect on seismicwave propagation are of fundamental intere st in many groundwater, engineering, and environmental studies. Rayleigh-wa ve phase velocity of a layered-earth model is a function of frequency and f our groups of earth properties: P-wave velocity, S-wave velocity, density, and thickness of layers. Analysis of the Jacobian matrix provides a measure of dispersion-curve sensitivity to earth properties. S-wave velocities are the dominant influence on a dispersion curve in a high-frequency range (>5 Hz) followed by layer thickness. An iterative solution technique to the we ighted equation proved very effective in the high-frequency range when usin g the Levenberg-Marquardt and singular-value decomposition techniques. Conv ergence of the weighted solution is guaranteed through selection of the dam ping factor using the Levenberg-Marquardt method. Synthetic examples demons trated calculation efficiency and stability of inverse procedures. We verif y our method using borehole S-wave velocity measurements.