A New Model for Vertical to Horizontal Response Spectral Ratios for Central and Eastern North America

Date: 4/25/2019

Time: 06:00 PM

Room: Grand Ballroom

It is a well-known fact that critical structures are required to be designed for the vertical effects of ground motions as well as the horizontal effects. We developed a new model for the spectral ratio of vertical to horizontal components of earthquakes (V/H ratio) for Central and Eastern North America (CENA). The proposed V/H ratio model has the advantage of considering the earthquake magnitude, source to site distance, and the shear-wave velocity of soil deposits in the upper 30m of the site for PGA and a wide range of periods (0.001 to 10.0 seconds). The model evaluation is based on a comprehensive set of regression analysis of the newly compiled Next Generation Attenuation (NGA-East) database of available CENA recordings with M ≥ 3.4 and R_RUP < 1000 km. The median value of the geometric mean of the orthogonal horizontal motions rotated through all possible nonredundant rotation angles, known as the GMRotD50 (Boore et al., 2006), is used along with the vertical component to perform regression using the nonlinear mixed effect regression. We excluded the earthquakes and recording stations in the Gulf Coast region due to their different ground-motion attenuation (Dreiling et al., 2014). To compute V/H ratios for the Gulf Coast region, we refer the readers to the study of Haji-Soltani et al. (2017) as an independent study performed on the Gulf Coast data. Moreover, we excluded the NEHRP site class E (soft-soil) sites from consideration because of their complex site-response characteristics and their potential for nonlinear site effects. Finally, we compared the predicted ratios from the proposed model with recently published V/H ratio models. We suggest our model be used for developing the vertical response spectra for CENA sites.

Presenting Author: Alireza Haji-Soltani

Authors