THE BOVEC (SLOVENIA) EARTHQUAKE,APRIL 1998: PRELIMINARY QUANTITATIVE ASSOCIATION AMONG DAMAGE,GROUND MOTION AMPLIFICATION AND BUILDING FREQUENCIES

After the 5.6 earthquake that struck Slovenia on Easter day in 1998, a quick survey was organised to perform a series of field measurements aimed at estimating site amplification. The possibility of recording aftershocks in the immediate aftermath of the main event improves the reliability of Nakamura's technique. The most affected sites that were sampled are located in the areas of Bovec and Dreznica. The damage pattern shows strong variations on short scale range. The typology of the buildings is very similar over the entire area being surveyed, and it is therefore likely that most of the variation could be attributed to site amplification effects. Local geology appears to be the dominant factor in most of the damage observed, and it can be qualitatively linked to empirical amplification functions obtained with Nakamura's technique. The damage enhancement between neighbouring sites is well correlated with amplification in a frequency range relevant to building vibration.