Combining active and passive multi-channel analysis of surface waves to improve reliability of VS,30 estimation using standard equipment

Surface wave methods are commonly used for seismic soil classification, however, their indirect nature implies a degree of uncertainty that needs to be described and constrained. To evaluate dispersive characteristics, we use active and passive sources, linear and circular arrays, and frequency-wavenumber analysis, spatial autocorrelation method and Roadside MASW analyses. We test the reliability of this approach in three different soil conditions of the Santiago basin (Chilean capital) using standard equipment. This methodology is compared with reliable results from high-energy active source and borehole information. To obtain a confident shear wave depth-profile with standard equipment, it is necessary to combine the dispersion curves obtained with low-energy active source, passive linear and circular arrays. Results obtained only through a passive linear test may not guarantee a reliable 30 m of exploration, especially when no high-traffic roads are present nearby. According to results obtained in the Santiago basin, we propose a methodology based on a combination of active and passive results.