Efficiency and Sufficiency of Ground Motion Intensity Measures in Predicting Ejecta Potential and Peak Pore Pressures

Abstract

This paper presents the results of 1520, three-dimensional (3D), fully-coupled, effective-stress, finite-element simulations in OpenSees to evaluate the influence of a variety of intensity measures (IMs) on excess pore pressures and potential for surface ejecta in the free-field. The analyzed profiles showcase different layering, and vertical changes in the groundwater table. We investigate the peak excess pore water pressure ratio in the middle of the liquefiable layer (peak r_u) and the ejecta potential index (EPI) as the primary engineering demand parameters (EDPs) of interest. A total of 20 IMs are considered as candidates, which represent a range of characteristics in terms of amplitude, frequency content, and duration of seismic loading. Efficiency, sufficiency, and predictability are used as the criteria to identify high-performing IMs for predicting the EDPs of interest. Based on the results from this preliminary parametric study, the average pseudo-spectral acceleration over the period range from 20% to 200% of the initial, small-strain site fundamental period, S_a,avg(0.2T_so, 2T_so) is identified as a high-performing IM for peak r_u in the free-field. For EPI predictions, the high-performing IM was found to be the cumulative absolute velocity (CAV). Both IMs were on outcropping rock.