Are Synthetic Accelerograms Suitable for Local Seismic Response Analyses at Near-Field Sites? Francesca Mancini *1 , Sebastiano D’Amico 2 , and Giovanna Vessia 3 ABSTRACT Local seismic response (LSR) studies are considerably conditioned by the seismic input fea- tures due to the nonlinear soil behavior under dynamic loading and the subsurface site conditions (e.g., mechanical properties of soils and rocks and geological setting). The selec- tion of the most suitable seismic input is a key point in LSR. Unfortunately, few recordings data are available at seismic stations in near-field areas. Then, synthetic accelerograms can be helpful in LSR analysis in urbanized near-field territories. Synthetic accelerograms are generated by simulation procedures that consider adequately supported hypotheses about the source mechanism at the seismotectonic region and the wave propagation path toward the surface. Hereafter, mainshocks recorded accelerograms at near-field seismic stations during the 2016–2017 Central Italy seismic sequence have been compared with synthetic accelerograms calculated by an extended finite-fault ground-motion simulation algorithm code. The outcomes show that synthetic seismograms can reproduce the high- frequency content of seismic waves at near-field areas. Then, in urbanized near-field areas, synthetic accelerograms can be fruitfully used in microzonation studies. KEY POINTS • Are stochastic simulations suitable for local seismic response analyses at near-field areas? • Results showed that simulations represent the high-fre- quency content of natural signals at near-field areas. • Synthetic signals can be profitably used in microzonation studies to predict local amplification effects. INTRODUCTION Local administration and national planning programs are pay- ing increasing attention to ground shaking and seismic site effects in urban centers especially set in near-field areas due to the large, differentiated damages occurring during the mod- erate-to-large earthquakes (M w > 5). Local site features can significantly affect the site response (Lanzo et al., 2019; Amanti et al., 2020) differently amplifying its seismic motion even at hundreds of meters distance and migrating it to a period or frequency range similar to those natural frequencies of buildings and infrastructures (commonly above 1 Hz) (Akinci et al., 2013; Panzera et al., 2016). Local seismic response (LSR) is related to many different coseismic phenom- ena: surface amplification due to the seismic impendence con- trast between soft soil deposits overlaying a rocky bedrock (D’Amico et al., 2008; Cox et al., 2011; Grasso and Maugeri 2012; Puglia et al., 2013; Pino et al., 2018), seismic-wave focali- zation due to basin-shaped bedrock (Frischknecht et al., 2005; Vessia et al., 2011; Rainone et al., 2013; Vessia and Russo, 2013; among others), topographic effects induced by soil and rock reliefs (Paolucci 2002; Primofiore et al., 2020; and references therein), slope instability (Lanzo et al., 2019), and liquefaction occurrence in which loose soil deposits lay under the ground- water level (e.g., Boncio et al., 2018). Thus, planning activities worldwide are nowadays involved in evaluating the LSR aiming at drawing microzoning maps (Vella et al. 2013; Panzera et al., 2017, 2019; Vessia et al., 2020, 2021). The aforementioned phenomena have been observed espe- cially at near-field areas also named by Boore (2014) as the fault damage zones (FDZs). These areas are where most of the heavy damages occur. Highly scattered seismic ground motions in FDZs are strongly dependent on the faulting mechanism, source directivity, and nonlinear soil behavior 1. International Research School of Planetary Sciences, University, “G. D’Annunzio” of Chieti-Pescara, Pescara, Italy, https://orcid.org/0000-0003-2410-0818 (FM); 2. Department of Geosciences, University of Malta, Msida MSD, Malta, https:// orcid.org/0000-0001-7429-4767 (SD); 3. Department of Engineering and Geology, University “G. D’Annunzio” of Chieti-Pescara, Chieti, Italy, https://orcid.org/0000- 0003-1733-7112 (GV) *Corresponding author: francesca.mancini@unich.it Cite this article as Mancini, F., S. D’Amico, and G. Vessia (2021). Are Synthetic Accelerograms Suitable for Local Seismic Response Analyses at Near-Field Sites? Bull. Seismol. Soc. Am. XX,1–16, doi: 10.1785/0120210074 © Seismological Society of America Volume XX Number XX – 2021 www.bssaonline.org Bulletin of the Seismological Society of America • 1 Downloaded from http://pubs.geoscienceworld.org/ssa/bssa/article-pdf/doi/10.1785/0120210074/5497014/bssa-2021074.1.pdf by Lumina Content Loader on 29 December 2021