Near‐surface VS structure by inversion of surface wave estimated from ambient seismic noise

Abstract

ABSTRACTIn this study, 20 hours of ambient seismic noise recorded from a small‐scale inter‐station distance was used to obtain near‐surface shear wave velocity structures at a local test site in Tehran (Iran). High‐resolution group velocity dispersion curves using fundamental mode of surface waves were calculated for all possible combinations of station pairs at frequencies ranging from 1 Hz to 25 Hz. Unlike most previous studies regarding ambient seismic noise, which observe very little coherent noise at frequencies larger than 1 Hz, the empirical Green’s functions were extracted using a root‐mean‐square stacking method showing more coherent signals. Our results indicate that ambient seismic noise is a viable technique at a frequency range of 1 Hz–25 Hz even when different sensor types are present. One‐dimensional VSV and VSH models from the near surface were then assessed by inverting the calculated Rayleigh and Love waves’ dispersion measurements. We observed that the calculated shear wave velocity model agrees with the available downhole model and shows three distinct layers in the upper 25 m of the test site.