A Ground-Motion Model for the Vertical Ground-Motion Component Based on Empirical Data from the NGA-East Data Set

ABSTRACT In this study, we propose a ground-motion model (GMM) to estimate vertical ground-motion components in central and eastern North America (CENA) using the referenced empirical method (REM) introduced by Atkinson (2008). The GMM developed in this study is the first vertical GMM for CENA using REM. To account for epistemic uncertainty in choosing a reference model, we considered three alternative models for the host region: Stewart et al. (2016), Gülerce et al. (2017), and Bozorgnia and Campbell (2016). We began by computing the vertical response spectrum for recorded motions in the Next Generation Attenuation-East Project data set. Next, we calculated residuals between the vertical-component pseudo-spectral accelerations from 0.01 to 10.00 s and the average predictions of the three reference models. We then applied a mixed-effects regression technique to derive adjustment factors for refining these predictions and to estimate the standard deviation components. The proposed GMM is assessed through residual analyses and comparisons with recorded data as a final step. The proposed GMM does not exhibit any discernible residual trends with distance and magnitude and appropriately accounts for site effects.