GNGTS 2013 - Atti del 32° Convegno Nazionale

Grimaz S., Cucchi F., Slejko D., Gattesco N., Pipan M., Barazza F., Biolchi S., Franceschinis R., Garcia J., Malisan P., Moretti A., Prizzon S., Rebeza A., Santulin M., Zini L.and Zorzini F.; 2012b: Il progetto ASSESS (Analisi degli scenari sismici degli edifici scolastici per la definizione delle priorità di intervento per la riduzione del rischio sismico): un esempio di stima del rischio sismico esportabile ad altre realtà nazionali. GEOITALIA, vol. 39, p. 27-35, ISSN: 1724-4285. Priolo, E., C. Barnaba, P. Bernardi, G. Bernardis, P. L. Bragato, G. Bressan, M. Candido, E. Cazzador, P. Di Bartolomeo, G. Durì, S. Gentili, A. Govoni, P. Klinc, S. Kravanja, G. Laurenzano, L. Lovisa, P. Marotta, F. Ponton, A. Restivo, M. Romanelli, A. Snidarcig, S. Urban, A. Vuan, and D. Zuliani (2005). Seismic monitoring in north-eastern Italy: A ten-year experience. Seismol. Res. Lett. 76, 446–454. Sandron D., Bragato P.L., Di Bernardo F., Di Narda N, Giordani D., Grimaz S., Miorin F., Pesaresi D., Primiero A., Rebez A. and Trocca C.; 2012: Civil protection municipal emergency plans: earthquake procedures in the frame of the Regional plan of emergencies in Friuli Venezia Giulia. In: Atti del 31° Convegno Nazionale GNGTS. Potenza, 20-22 Novembre 2012. p. 371-378, ISBN: 978-88-902101-2-9, Potenza, 20-22 Novembre 2012. Slejko D., Grimaz S., Cucchi F., Gattesco N., Pipan M., Barazza F., Biolchi S., Franceschinis R., Garcia J., Malisan P., Moretti A., Prizzon S., Rebez A., Santulin M., Zini L. and Zorzini F.; 2012: Seismic risk of schools at a regional scale: the ASSESS project. In: SISMOS 2012, por una gestión stratégica de riesgos de desasters. Paper C1, Santiago de Cuba: Universitad de Oriente, ISBN: 978-959-207-449-1, Santiago de Cuba, 8-11 May 2012. Shortcomings of the current assessment of seismic hazard: examples from some Italian regions M. Viti 1 , D. Babbucci 1 , M. Baglione 2 , N. Cenni 3 , V. D’Intinosante 2 , E. Mantovani 1 , L. Martelli 4 , C. Tamburelli 1 1 Dipartimento di Scienze Fisiche, della Terra e dell’Ambiente, Università di Siena, Italy 2 Coordinamento Regionale Prevenzione Sismica, Regione Toscana, Italy 3 Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Bologna, Italy 4 Servizio Geologico, Sismico e dei Suoli, Regione Emilia-Romagna, Italy 1. Introduction. It is well known that, both in Italy and in the rest of the world, the assessment of seismic hazard is currently carried out by probabilistic approaches, indicated as Probabilistic Seismic Hazard Assessment (PSHA). Such procedure, implemented over the last four decades, estimates the parameters of ground motion, as the Peak Ground Acceleration (PGA). This methodology takes into account the frequency of seismic events occurring at the seismogenic sources recognized in the study area, as deduced from seismic history. Moreover, the effects caused by each shock are estimated by empirical relationships, describing the attenuation of ground motion with the distance from the hypocenter to the site of interest. The consequences of the destructive earthquakes occurred worldwide in the last decade have cast doubts about the reliability of the above methodology, also inducing some authors to suggest a substantial revision of the probabilistic approach, in order to achieve a more realistic estimate of seismic hazard (e.g., Stein et al. , 2012 and references therein). Taking into account the above suggestion, this study is aimed at focusing the main shortcomings of the PSHA, with particular attention to the assessment of seismic hazard in four administrative regions of central-northern Italy (Emilia-Romagna, Toscana, Umbria and Marche). Description of the PSHA. The PSHA develops by four distinct, consecutive phases (e.g., Cornell, 1968; McGuire, 1978; Algermissen e Perkins, 1976; Reiter, 1990; Frankel et al. , 2000). In the first phase, it is assumed that the seismicity of the study area is generated by some seismic sources, usually schematized by polygons including recognized (or presumed) active fault systems. For the Italian region, the previous ZS4 seismic zoning (Meletti et al. , 2000) has been replaced by the ZS9 model, formed by 36 major seismogenic zones (Meletti et al. , 2008). In the second phase, a set of parameters characterising the seismic activity, as e.g. the maximum expected magnitude M max , is assigned to each of the above zones. Moreover, for each value of magnitude, from the damage threshold to M max , the number of earthquakes expected in a given time interval is computed. Indeed, the so-called “seismic scenario” is represented by 474 GNGTS 2013 S essione 2.3