GNGTS 2013 - Atti del 32° Convegno Nazionale

We observed that the effect of the rupture directivity is to increase the seismic hazard estimations up to 25% and predict a reduction up to 10% in the southern Apennines. The effectiveness of the correction for directivity depends on the period of the spectral acceleration. Its effect is lower at shorter periods. The strategy proposed in this work has the advantage that it is suitable to be updated anytime that a new information is available from catalogs; as an example, in this preliminary study the nucleation position was fixed to the value which gave the maximum correction at the considered site; however it is possible to vary the nucleation position inside the sub-fault by assigning a proper density distribution which is not necessarily uniform (Mai et al. , 2005). Moreover, the incorporation of the Spudich and Chiou (2008)’s corrective factor is able to predict the spatial variability of ground motion due to rupture complexity even in regions where a specification of the directivity effect is not directly available from observations. Our results show that the complexity of the rupture process is effective also in presence of small faults, thanks to the probabilistic treatment of a physical process. Acknowledgements. This study is supported by the Dipartimento della Protezione Civile (DPC) funds of the project INGV-DPC 2012 S2 “Constraining Observations into Seismic Hazard” coordinated by Laura Peruzza. The final results released by this study can be found at the web site address: https://sites.google.com/site/ingvdpc2012progettos2/ deliverables/d5_2. References Abrahamson, N.A. (2000), Effects of rupture directivity on probabilistic seismic hazard analysis, Proceedings of the 6 th International Conference on Seismic Zonation , Palm Springs, CA, Earthquake Engineering Research Institute (EERI). Akkar, S. and Bommer, J.J., 2010. Empirical equations for the prediction of PGA, PGV, and spectral accelerations in Europe, the Mediterranean, and the Middle East. Seismological Research Letters, 81(2), pp. 195-206. Basili, R., G. Valensise, P. Vannoli, P. Burrato, U. Fracassi, S. Mariano, M. M. Tiberti, and E. Boschi, 2008. The Database of Individual Seismogenic Sources (DISS), version 3: Summarizing 20 years of research on Italy’s earthquake geology, Tectonophysics, 453, pp. 20-43 Bindi D., Pacor F., Luzi L., Puglia R., Massa M., Ameri G., Paolucci R., 2011. Ground motion prediction equations derived from the Italian strong motion database, Bulletin of Earthquake Engineering, 9, pp. 1899-1920 Ben-Menahem, A., 1961. Radiation of seismic surface-waves from finite moving sources, PhD thesis, California Institute of Technology. Benioff, H.,1955. Earthquakes in Kern County California during 1952, Department of natural resources - Division of Mines, 171, pp. 199-204. Bernard P. and Madariaga R., 1984. A new asymptotic method for the modelling of near-field accelerograms, Bulletin of the Seismological Society of America, 74, pp. 539-557 Boore D. M. & Atkinson G. A., 2008. Ground Motion prediction equations for the average horizontal component of PGA, PGV, PGD, and 5\% damped PSA art spectral periods between 0.01 s and 10.0 s, Earthquake Spectra, 24(1), pp. 99-138. Brune, J.N. 1968. Seismic moment, seismicity and rate of slip along major fault zones, J. Geophys. Res. 73, 777-784. Cauzzi, C. and E., Faccioli, 2008. Broadband (0.05 to 20s) prediction of displacement response spectra based on worldwide digital records,Journal of Seismology, 12, pp. 453-475. Chiocciarelli E. and I. Iervolino, 2013. Near source seismic hazard and design scenarios Earthquake Engineering & Structural Dynamics, 42, pp. 603-622. Kasahara, K., 1960. An Attempt to Detect Azimuth Effect on Spectral Structures of Seismic Waves (The Alaskan Earthquakes of April 7, 1958), Bulletin of Earthquake Research Institute, 38, pp. 207-218. Power M., Chiou B., Abrahamson N., Bozorgnia Y., Shantz T. & Roblee C., 2008. An overview of the NGA Project, Earthquake Spectra, 24, pp. 3-21. Rowshandel, B., 2006. Incorporating Source Rupture Characteristic into Ground-Motion Hazard Analysis Models Seismological Research Letters, 77, pp. 708-722. Somerville P.G. and N.F. Smith and R.W. Graves, 1997. Modification of empirical Strong Ground motion Attenuation Relations to include the Amplitude and Duration Effects of rupture Directivity, Seismological Research Letters, 68, pp. 199-222. Spagnuolo E., Herrero A. & Cultrera G., 2012. The effect of directivity in a PSHA framework Geophysical Journal International, 191(2), pp. 616-626 Spudich, P. and Chiou, B. S., 2008. Directivity in NGA Earthquake Ground Motions: Analysis Using Isochrone Theory, Earthquake Spectra, 24(1), pp. 279-298. Spudich, P. and Frazer, L., 1984. Use of ray theory to calculate high-frequency radiation from earthquake sources having spatially variable rupture velocity and stress drop, Bulletin of the Seismological Society of America, 74(6), pp. 2061- 2082. 145 GNGTS 2013 S essione 2.1