Estimation of Shear-Wave Velocity Profiles: Inversion of Spatial Autocorrelation Coefficients

Microtremors are measured and analized by spatial autocorrelation method (SPAC) for determination of shear-wave velocity (Vs) models. In SPAC method, estimating Vs profiles is a two-stage process. Conventionally, Rayleigh wave phase velocity dispersion data, which are obtained from SPAC coefficients, are inverted for the shear-wave velocity models. In this study, a more practical (one-stage) scheme is utilized where the SPAC coefficients are directly inverted for unknown shear-wave velocities. The method is based on a weighted damped-least squares solution. Stability of inversion is achieved by using differential smoothing approach that provides Vs models in which the velocity differences between adjacent layers are minimized.