The NGA-W1 Vertical-to-Horizontal Spectral Acceleration Ratio Prediction Equations Adjusted for Turkey

Abstract

Online Material: Supplemental tables. Vertical ground motions are considered in the seismic design of critical structures such as nuclear power plants and dams. Results of a recent study revealed that the effect of vertical component ground motion on the seismic response of ordinary highway bridges is also significant, especially in near‐fault regions (Gulerce and Abrahamson, 2010; Gulerce et al. , 2012). In the probabilistic seismic‐hazard assessment (PSHA) environment, site‐specific vertical design spectra may be developed by computing the hazard independently for the vertical ground‐motion component, which in fact requires accurate prediction of vertical component ground‐motion intensity measures. However; new and updated vertical ground‐motion‐prediction equations (GMPEs) are not available for the western United States or for other active tectonic regions such as Turkey. Also, conducting separate vertical and horizontal component PSHAs may lead to inconsistent horizontal and vertical spectra due to the different distance and magnitude scaling and different standard‐deviation values of vertical GMPEs compared with horizontal GMPEs. The alternative approach is to use empirical vertical‐to‐horizontal spectral acceleration ratio (V/H ratio) prediction models to scale the horizontal spectrum that is developed using the results of horizontal component PSHA. Empirical V/H ratio predictive models may be built by developing separate vertical and horizontal GMPEs and then computing the ratio for a given magnitude and distance. In their studies, both Bozorgnia and Campbell (2004) and Bindi et al. (2009) used this approach on different sets of ground‐motion data. Recent predictive models derived by Bommer et al. (2011), Edwards et al. (2011), and Gulerce and Abrahamson (2011) were based on the directly calculated V/H ratios. However, datasets used by these developers, functional forms, and range of applicability of their models is considerably different. The database of Bommer et al. (2011) model includes 1267 ground motions from 392 earthquakes that occurred in Europe and surrounding regions within …