Soil classification in 15 accelerographic stations using methods based on ambient vibrations and Vs30

Abstract

The H/V, FK and SPAC techniques were applied , all based on the measurement of ambient vibrations generated by surface waves for the characterization of soils beneath 15 selected sites, 12 of them corresponding to accelerographic stations of the Earthquake Engineering Laboratory of the University of Costa Rica. To achieve this, sensors (triaxial geophones) were placed in circular arrays and spectral ratios (from H/V) dispersion curves (from FK) and autocorrelation curves (from SPAC) for each site were obtained. Based on the above, the soil type was determined according to the characteristic site period (T₀) read from H/V and criteria according to Zhao et al. (2006). Each site was also classified according to the Seismic Code of Costa Rica (2010) and Vs30 parameter calculated from the inversion of dispersion and autocorrelation curves. T₀ values from 0.3 s to 1.5 s and Vs30 between 244 m/s to 379 m/s were obtained, indicating that soils correspond to S3 (soft soil, 67% of all cases). No site whose classification corresponds to S₁ (rock) or S₄ (very soft soil) was found