Damping Scaling Factors for Vertical Elastic Response Spectra for Shallow Crustal Earthquakes in Active Tectonic Regions

Abstract

This paper develops a new model for a damping scaling factor (DSF) that can be used to adjust elastic response spectral ordinates for the vertical component of earthquake ground motion at a 5% viscous damping ratio to ordinates at damping ratios between 0.5% and 30%. Using the extensive NGA-West2 database of recorded ground motions from worldwide shallow crustal earthquakes in active tectonic regions, a functional form for the median DSF is proposed that depends on the damping ratio, spectral period, earthquake magnitude, and distance. Standard deviation is a function of the damping ratio and spectral period. The proposed model is compared to the DSF for the “average” horizontal component. In general, the peak in DSF is shifted toward shorter periods and is farther from unity for the vertical component. Also, the standard deviation of DSF for vertical motion is slightly higher than that observed for the “average” horizontal component.