Updating the Site Response Analyses at San Giuliano di Puglia (CB), Italy

On the morning of October 31st, 2002, an M-w=5.74 earthquake hit the Molise Region, Italy. The epicenter was located near the village of San Giuliano di Puglia, approximately 200 km E of Rome. This moderate earthquake has a worldwide relevance due to the collapse of the "F. Jovine" elementary school and the death of 27 pupils and a teacher. This earthquake represented a turning point for Earthquake Engineering in Italy since it pushed the development of updated seismic codes, a review for the seismic hazard and it boosted the whole research in Earthquake Engineering in the country.Soon after the earthquake, the strongly non-uniform damage distribution observed in San Giuliano di Puglia suggested that site amplification significantly affected the seismic response of the town.For this reason, in the aftermath of the earthquake and for almost a decade, very detailed soil investigations and numerical analyses were carried out to understand the possible site effects in the village, in the framework of different studies and research projects.In this wide body of research, the crucial role played by soil investigation and monitoring was already strongly pointed out. Therefore, it was challenging to check if more recent data, including new geotechnical tests and more recent recordings, would either confirm the previous findings or highlight the need to develop new subsoil models with the aim to detect the spatial distribution of the related ground motion amplification.In the paper, it is first summarized the state-of-the-art about site effects in San Giuliano di Puglia. Then, the new shear wave velocity profiles and the peculiar seismic monitoring system that was deployed in the village are critically described. The recent data collected by the stations are presented and numerical models are analyzed to reproduce the recorded signals.It has been confirmed that 1-D models are not able to reproduce the observed seismograms.The availability of new information leads to a partial re-evaluation of the subsoil model for San Giuliano di Puglia and, particularly, it was necessary to consider a higher small-strain stiffness for some soil strata to achieve an acceptable congruence between models and experimental data.The need for specific studies to evaluate the seismic actions for design is finally highlighted by comparing numerically computed elastic response spectra with those proposed by the new technical code for construction and by seismic microzonation studies.The research confirmed that the reliability of the geotechnical characterization is an essential element for solving earthquake geotechnical engineering problems. In addition, the geotechnical characterization can be significantly improved by the added-value provided by accelerometer stations, arranged in vertical arrays.