Recent developments in vertical ground motion models for engineering applications in Italy

This work provides an overview of recent developments of empirical ground-motion modeling (GMMs) for the vertical component of seismic ground motions in Italy, with special attention to near-source conditions. The motivation comes from the growing interest in using the vertical component for earthquake engineering applications, such as ground-motion simulation, source characterization, selection of multi-components spectrum compatible records for dynamic analysis, where amplitude, frequency content and consistency with horizontal components are key elements. The GMMs set, briefly called ITA18, allows to predict several parameters such as peak ground acceleration (PGA) and velocity (PGV), acceleration response spectra (SA) and Fourier Amplitude Spectrum (FAS). SA predictions are provided for spectral ordinates in the range of periods 0.01-10s, while FAS for the frequency range 0.1-30Hz, allowing detailed spectral analysis. The models are calibrated using a comprehensive and quality-checked collection of strong-motion recordings from shallow crustal events, mainly in Italy, covering a wide range of magnitudes, source-to-site distances, and site conditions (Vs30). Near-source data were included considering the NESS 1.0 (Pacor et al. 2021) dataset a global collection of recordings of large magnitude earthquakes. The models are consistent with the previously published GMMs for the horizontal component (Lanzano et al. 2019; Lanzano et al. 2022). An application example using fully consistent horizontal and vertical target spectra is presented to demonstrate the practical applicability of the VH model for the spectrum-compatible selection of recorded ground motions.