Variability of site geophysical exploration results using surface wave methods

Abstract

After the 2010 Maule earthquake (Mw 8.8) major changes were made in seismic regulations at the
national level. One of the most interesting aspects was the change in the methodology for the soil classification
in the NCh433 design standard. In summary, there was a transition from the use of soil strength parameters
to soil dynamic parameters, such as the harmonic average of the shear wave velocity in the first 30 m of
the subsoil (Vs30) and the predominant period (Tg), whose incorporation is under review. In this study, results from
4 teams exploring the same 6 sites using various sensors, geometries, and procedures are compared, all of them
using Surface Wave Methods (MOS, for its initials in Spanish). It is concluded that, in general, the estimation
of Vs30 and Tg are quite robust, but important variations are observed in the shear wave velocity profiles obtained.
For that reason, it is necessary the comparison of these results with the stratigraphy. These results point to the
limitations and potential of MOS to estimate the dynamic properties of sites.