GNGTS 2014 - Atti del 33° Convegno Nazionale

78 GNGTS 2014 S essione 2.1 Slejko D., Peruzza L. and Rebez A.; 1998: Seismic hazard maps of Italy . Annali di Geofisica, 41 , 183-214. Slejko D, Carulli G.B., Riuscetti M., Cucchi F., Grimaz S., Rebez A., Accaino F., Affatato A., Biolchi S., Nieto D., Puntel E., Sanò T., Santulin M., Tinivella U. and Zini L.; 2011: Soil characterization and seismic hazard maps for the Friuli Venezia Giulia region (NE Italy) . Boll. Geof. Teor. Appl., 52 , 59-104. Standards New Zealand; 2004: Structural design actions. Part 5: Earthquake actions in New Zealand . Standards New Zealand, Wellington. Toro G.R., Abrahamson N.A. and Schneider J.F.; 1997: Model of strong motions from earthquakes in central and eastern North America: best estimates and uncertainties . Seism. Res. Lett., 68 , 41-57. Utsu T.; 1965: A method for determining the value of b in the formula logN=a-bM showing the magnitude-frequency relation for earthquakes . Geophys. Bull. Hokkaido Univ., 13 , 99-103. Utsu T.; 1966: A statistical significance test of the difference in b-value between two earthquake groups . J. Phys. Earth, 14 , 37-40. Weichert D.H.; 1980: Estimation of the earthquake recurrence parameters for unequal observation periods for different magnitudes . Bull. Seismol. Soc. Am., 70 , 1337-1346. Wells D.L. and Coppersmith K.J.; 1994: New empirical relationship among magnitude, rupture length, rupture width, rupture area, and surface displacement . Bull. Seism. Soc. Am., 84 , 974-1002. Yang J. and Sato T.; 2000: Interpretation of seismic vertical amplification observed at an array site. Bull. Seism. Soc. Am. , 90 , 275-285. REVISION OF SEISMIC HAZARD IN EMILIA-ROMAGNA BASED ON A NEW SEISMOGENIC ZONATION OF THE NORTHERN APENNINES M. Santulin 1 , A. Tamaro 1 , A. Rebez 1 , L. Martelli 2 , F. Sani 3 , M. Bonini 4 , G. Corti 4 , D. Sandron 1 , D. Slejko 1 1 OGS - Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Trieste, Italy 2 Servizio Geologico, Sismico e dei Suoli, Regione Emilia-Romagna, Bologna, Italy 3 Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Italy 4 Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche, Firenze, Italy Introduction . Recent events in the Emilia-Romagna region highlighted unexpected large ground motions and this aspect caused criticism to the estimates obtained by probabilistic seismic hazard analyses represented by the national seismic hazard maps MPS04 (Stucchi et al. , 2011). For this reason, some regional seismotectonic studies are in progress for this area, and a preliminary version of a new regional seismogenic zonation (see Fig. 1a) has been proposed (Martelli et al. , 2014). This new zonation is, in the studied area, intentionally more detailed if compared to the national one (Meletti et al. , 2008) that has been conceived to cover the entire Italian territory. The introduction of two SW-NE transfer zones cutting the NW-SE trend of the Apennine zones of the national zonation represents the major novelty for the Emilia-Romagna region. ��� ����� �� ���� �� ��������� ��� ����������� ���������� �� ���� ������� ������������� �� The boxes of Fig. 1a represent the superficial projection of rock volumes characterized by homogeneous deformation inside (in terms of failure mechanisms and geometry of faults: depth range, strike and dip). �� ��� ������� ����� � ������������� ������� ������ �������� ������ ��� In the present work, a probabilistic seismic hazard analysis (PSHA) has been conducted aiming at comparing the seismic hazard estimates based on the new zonation [obtained according to Cornell (1968) in the software formulation of Crisis 2012 (Ordaz et al. , 2012)] with the national ones. In agreement with the Italian zonation, also the new seismogenic zones (SZs) have been initially considered in 2D. Successively, a 3D geometry has been defined for the new zones by introducing some seismogenic planes, i.e., 3D surfaces with a geometry in agreement with the tectonic style dominating in the SZ. The new hazard estimates, although very preliminary, show interesting differences with respect to the national ones and point out the influence of a 3D geometry joint with a proper attenuation model in the expected ground motions on the surface. Summary of the new seismogenic zonation for the northern Apennines . Since the publication the Italian seismogenic zonation ZS9 of Meletti and Valensise (2004) (see also