S-Wave Velocity Profiling by Joint Inversion of Microtremor Dispersion Curve and Horizontal-to-Vertical (H/V) Spectrum

A joint inverse analysis using both microtremor dispersion curve and horizontal-to-vertical (H/V) spectrum is proposed for estimating the S-wave velocity (VS) profiles of subsurface soils. In the inversion, both microtremor dispersion and H/V data are assumed to be the Rayleigh-wave dispersion curve and the surface (both Rayleigh and Love) wave H/V spectrum that have been theoretically derived by taking into account the effects of their fundamental and higher modes. The proposed joint inversion as well as the conventional one using dispersion data alone is per- formed at four sites where shallow VS profiles down to engineering bedrock are available. The VS profiles estimated by the proposed joint inversion are more con- sistent with available down-hole velocity logs than those by the conventional method. In particular, the proposed inversion shows significant improvement in estimating bedrock VS structures compared to the conventional inversion. Sensitivity analyses indicate that the surface-wave H/V ratio is sensitive to the bedrock VS structure more than the Rayleigh-wave phase velocity, confirming that the proposed joint inversion including H/V spectrum is promising.