GNGTS 2021 - Atti del 39° Convegno Nazionale

GNGTS 2021 S essione 2.2 338 Conclusions This study proposes a novel empirical GMM for VH response spectral accelerations (up to 10 s), PGA and PGV for shallow crustal earthquakes in Italy. The model is based on the ITA18 dataset and it includes a median corrective factor for near-source effects, calibrated on the near-source strong motion dataset NESS1.0. The inclusion of such correction factor allows to overcome the limitations of a model calibrated solely on the ITA18 dataset, which is found to yield bias on the unsafe side because of the scarcity of data at short source-to-site distances. As a matter of fact, the ITA18-NESS model (reference model plus corrective term) provides higher VH spectra espe- cially at distances less than 10 km and for M w larger than 6.5. Vertical predictions of the proposed model, with and without the corrective term, are verified against the available observations from both ITA18 and NESS1.0 datasets for selected scenarios, confirming a good predictive capacity of the model. Furthermore, the comparison with indepen- dent empirical GMMs shows a comparable behavior both in terms of median estimates, especial- ly for rock and stiff soil sites, and sigma values. However, for very soft sites, the empirical models accounting for non-linear site response exhibit a higher amplification of VH ratios for large M w and short distance scenarios. Complete List of Authors: Ramadan, Fadel; fadel.ramadan@mail.polimi.it Smerzini, Chiara: chiara.smerzini@polimi.it Lanzano, Giovanni: giovanni.lanzano@ingv.it Pacor, Francesca: francesca.pacor@ingv.it References: Akkar S., Sandikkaya M.A., Ay B.Ö. Compatible ground-motion prediction equations for damping scaling factors and vertical-to-horizontal spectral amplitude ratios for the broader Europe region. Bulletin of Earthquake Engineering 2014; 12: 517-547. Atkinson G.M. Ground-motion prediction equations for eastern north america from a referenced empirical approach: implications for epistemic uncertainty. Bulletin of the Seismological Society of America 2008; 98(3): 1304-1318. Atkinson G.M. Ground-Motion Prediction Equations for Hawaii from a Referenced Empirical Approach. Bulletin of the Seismological Society of America 2010; 100(2): 751-761. Bommer J.J., Akkar S., Kale Ö. A model for vertical-to-horizontal response spectral ratios for Europe and the Middle East. Bulletin of the Seismological Society of America 2011; 101(4): 1783-1806. Bozorgnia Y., Campbell K.W. Vertical ground motion model for PGA, PGV, and linear response spectra using the NGA-West2 database. Earthquake Spectra 2016; 32(2): 979-1004. Bozorgnia Y., Campbell K.W. Ground motion model for the vertical-to-horizontal (V/H) ratios of PGA, PGV, and response spectra. Earthquake Spectra 2016; 32(2): 951-978. Chiou B.S.-J., Youngs R.R. NGA-West2 ground motion prediction equations for vertical ground motions. PEER Report 2013/24: 127-161. Di Michele F., Cantagallo C., Spacone E. Effects of the vertical seismic component on seismic performance of an unreinforced masonry structures. Bulletin of Earthquake Engineering 2020; 18: 1635–1656. Gülerce Z., Abrahamson, N.A. Site-specific design spectra for vertical ground motion. Earthquake Spectra 2011; 27(4): 1023-1047. Gülerce Z., Kamai R., Abrahamson N.A., Silva W.J. Ground motion prediction equations for the vertical ground motion component based on the NGA-W2 database. Earthquake Spectra 2017; 33(2): 499-528. Kamai R.N., Abrahamson N.A., Silva W.J. Nonlinear horizontal site amplification for constraining the NGA- West2 GMPEs. Earthquake Spectra 2014; 30(3): 1223-1240.