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

Abstract

Surfacewave 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 circulararrays, and frequency-wavenumber analysis, spatial autocorrelation method and RoadsideMASW analyses. We test the reliability of this approach in three different soil conditions ofthe Santiago basin (Chilean capital) using standard equipment. This methodology is comparedwith reliable results from high-energy active source and borehole information. To obtain aconfident shear wave depth-profile with standard equipment, it is necessary to combine thedispersion 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 30m ofexploration, especially when no high-traffic roads are present nearby. According to resultsobtained in the Santiago basin, we propose a methodology based on a combination of activeand passive results.