Ground-motion models for predicting vertical components of PGA, PGV and 5%-damped spectral acceleration (0.01-10s) in Iran

This paper presents ground motion models to predict vertical components of peak ground acceleration, peak ground velocity, and 5%-damped response spectral acceleration at periods ranging from 0.01 to 10s. These models are derived from the comprehensive Iranian strong ground-motion database containing 1350 three-component time-histories recorded during 370 earthquakes with 4.5Mw7.4. Possible regional dependency of vertical ground-motions to characteristics of three seismo-tectonic regions in Iran was investigated through analysis of variance (ANOVA) technique. Consistent models based on four distance measures; two for point-source (Repi and Rhyp) and two for finite-fault (RJB and Rrup), were developed. The distribution of inter and intra-event residuals presents satisfactory agreement between actual data and our proposed vertical ground motion prediction equation (GMPE). Furthermore, a detailed comparison between our predictions and four local and global GMPEs is presented, well as horizontal model of Darzi et al. (Bull Seismol Soc Am. 10.1785/0120180196, 2018). In addition, this study provides period-dependent correlation coefficients between epsilons of different GMPEs corresponds to either horizontal, vertical, or vertical-to-horizontal spectral ratio intensity measures as a function of single or two-periods of interest.