GNGTS 2014 - Atti del 33° Convegno Nazionale

84 GNGTS 2014 S essione 2.1 We are aware that also the model obtained in this way, which introduces one or maximum two SPs inside each SZ, is a simplification of a much more complicated reality, but it can be seen as the first step towards a fault characterization of the study region. It has to be noted that the superficial projection of these modelled SPs covers again the whole width of the SZ. The geological characterization of each SZ (Tab. 1) suggests also the percentage of activity pertinent to each SP (when more than one are present in the same SZ). Consequently, the G-R distribution of seismicity has been partitioned accordingly. The final seismic hazard map here presented (Fig. 3a) takes into account all the tectonic features pinpointed by the new seismogenic zonation (Martelli et al. , 2014): each SP is defined by a 3D geometry and has defined a tectonic style which is taken into account by associating the suitable C&F GMPE. Fig. 3a clearly emphasises the deep geometry and the tectonic style of the SPs; the highest expected ground motion (between 0.2 and 0.3 g) remains located in the SZ Romagna Apennines-Po Plain Margin, Romagna Apennines and Mugello, similarly to the elaboration with simplified SPs (Fig. 2b). With respect to that previous elaboration, the SZ 911mod looses importance while the SZ Garfagnana is characterized by a higher PGA. It is worth noting that all these details cannot be seen in the map of Fig. 2c, because of the larger size of the SZs considered. A comparison could be attempted with the new European seismic hazard map developed in the framework of the SHARE project and recently released (SHARE, 2014). The SHARE map was computed on the basis of a sophisticated logic tree which considered 3 different models for the seismogenic sources. The resulting map, reproduced in Fig. 3b, shows a wide area with expected PGA between 0.2 and 0.3 g covering the large part of the Emilia – Romagna region. The difference between the two maps is displayed in Fig. 3c. Final comments. The application to the seismic hazard estimates of the new seismogenic zonation proposed for the northern Apennines represents an interesting effort towards a new definition of the seismogenic sources, more detailed than the usual plain surfaces but more general than the individual faults. This new types of sources, here defined as SPs, overcome the dilemma about the applicability of a characteristic earthquake model for the Italian tectonic context because the G-R seismicity model is surely more suitable for sources collecting several faults inside. The final elaboration here presented is very preliminary and more science must be considered before considering it really an alternative map to the consolidated MPS04 one, but it represent an alternative way to consider the seismogenic sources in PSHA. Acknowledgements. Many thanks are due to Daniela Di Bucci, Civil Protection Department, for her very detailed review that has strongly improved this paper. References Basili R., Valensise G., Vannoli P., Burrato P., Fracassi U., Mariano S., Tiberti M.M. and Boschi E.; 2008: The Database of Individual Seismogenic Sources (DISS), version 3: summarizing 20 years of research on Italy’s earthquake geology . ��������������� Tectonophysics, 453 , 20–43. Boccaletti M. and Martelli L. (a cura di); 2004: Carta sismotettonica della Regione Emilia-Romagna, scala 1:250.000 e note illustrative . Selca, Firenze. Boccaletti M., Calamita F. and Viandante M.G.; 2005: La Neo-Catena litosferica appenninica nata a partire dal Pliocene inferiore come espressione della convergenza Africa-Europa . ����� ���� ����� ���� Boll. Soc. Geol. It., 124 , 87-105. Boccaletti M., Corti G. and Martelli L.; 2011: Recent and active tectonics of the external zone of the Northern Apennines (Italy) . ���� �� ����� ���� ������������ ����������� ���� �������������������������� Int. J. Earth Sci. (Geologische Rundschau), doi: 10.1007/s00531-010-0545-y. Castello B., Selvaggi G., Chiarabba C. andAmatoA.; 2006: CSI Catalogo della sismicità italiana 1981-2002 , versione 1.1. ��������� ����� ����������������������� � INGV-CNT, Roma, <http://csi.rm.ingv.it> . Cauzzi C. and Faccioli E.; 2008: Broadband (0.05 to 20 s) prediction of displacement response spectra based on worldwide digital records . J. Seismol., 12 , 453-475. Cornell C.A.; 1968: Engineering seismic risk analysis . Bull. ������ ���� ���� Seism. Soc. Am., 58 , 1583-1606. DGR; 2014: Approvazione di accordo di collaborazione istituzionale con l’Istituto Nazionale di Oceanografia e Geofisica Sperimentale e con il consorzio interuniversitario ReLUIS per la realizzazione di studi finalizzati all’aggiornamento delle mappe di pericolosità e vulnerabilità sismica del territorio regionale . Deliberazione di Giunta della Regione Emilia-Romagna n. 175 del 17 febbraio 2014.