GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 2.1 GNGTS 2024 A data-driven parametrization of source-directivity effects: the study case of Central Italy L. Colavitti 1,2 , G. Lanzano 1 , S. Sgobba 1 , F. Pacor 1 1 National Institute of Geophysics and Volcanology, INGV Seismology applied to Engineering (Milan, Italy) 2 University of Genoa, DISTAV Department of Earth, Environment and Life Sciences (Genoa, Italy) INTRODUCTION Assessing the spatial variability of seismic shaking in the epicenter zone is one of the major challenges to be addressed in seismic hazard estimates and ground motion scenarios generation. Among the various contributions causing the azimuthal variation of the shaking, source directivity plays a crucial role. As already proven by recent research, directivity effects, which are related to the characteristics of rupture propagation along the fault, can provoke ground motion amplifications in wider or narrower frequency ranges, even in small to moderate magnitude earthquakes ( López-Comino et al., 2012 ; Pacor et al. 2016 ; Convertito et al. 2016 ). The scope of this work is to construct a fully data-driven directivity predictive model that can be used to estimate seismic ground motion amplification, using few independent parameters. DATA AND METHOD The dataset used in this research is the same used by Sgobba et al. (2021a) and Colavitti et al. (2022) and is formed by high-quality waveforms of Central Italy covering the period range from 2009 to 2018. In particular, we analyzed about 35,000 recordings from 460 stations ( Fig. 1a ) and 456 events ( Fig. 1b ), for which we computed the 5% acceleration elastic response spectra ordinates from 0.04 to 2 sec for shallow active crustal events ( Spallarossa et al., 2023 ). The events spans from magnitude values between 3.2 and 6.5, and contain earthquakes of the sequence of L’Aquila in 2009 ( Ameri et al., 2009 ; Calderoni et al., 2015 ) and Amatrice-Visso-Norcia in 2016-2017 ( Chiaraluce et al., 2017 ; Michele et al., 2020 ). The method to detect the effects of source directivity is the same implemented for the ordinates of the Fourier Amplitude Spectra (FAS) by Colavitti et al. (2022) and is based on the analysis of the residuals obtained from non-ergodic ground motion modelling. In particular, we identify the