The 1998 Umbro-Marchigiano earthquake induced heavy damage to the building heritage of the historic centre and of the hamlets of Norera Urnbra (Perugia, Italy). Even the hamlet of Isola, 4 kmfrom Nocera Umbra, suffered pronounced damage; most buildings either collapsed or were badly damaged, in spite of the fact that they had recently been renovated in conformity to the criteria suggested in the Italian seismic code. Also the values of the peak ground acceleration recorded during the two main shocks of the seismic sequence at the arrelerometric station located about 1000m from the historical centre of Nocera Umbra were particularly high and evidenced an important influence of local site conditions of the area on the ground surface motion.

Within the framework of the microzonation project developed after the earthquake, several boreholes with undisturbed sampling, laboratory geotechnical tests for measuring static and dynamic soil properties, and field geophysical tests to evaluate small strain soil stiffness, were performed in the area of Nocera Umbra and of its hamlets. Therefore, soil deposit conditions under the accelerometric station were defined and a deconvolution analysis of the recorded seismic signals was carried out. Analyses of ground motion were then performed in two sites of the hamlet of Isola with the deconvolved motions on rock outcrop. The results of this experimental and analytical study are described in this paper.

    The 1998 Umbro-M …

AUTORI: Crespellani T., Madiai C., Simoni G. Vannucchi G. RIG ANNO: 2000 NUMERO: 4 Numero di pagina: 39



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