Identification of optimal ground-motion intensity measures for assessing liquefaction triggering and lateral displacement of liquefiable sloping grounds

Abstract

This article aims at identifying the optimal scalar- and vector-valued intensity measures (IMs) for predicting liquefaction triggering and the consequence of liquefaction (i.e. permanent deformation of sloping grounds), respectively. A total of 169 ground motions were selected from the NGA-West2 database. Using the selected ground motions as input, one-dimensional dynamic analyses were conducted for generic sloping ground soil profiles consisting of a loose-sand liquefiable layer implemented in OpenSees. The excess pore water pressure ratio and the liquefaction-induced lateral displacement were regarded as the engineering demand parameters (EDPs) of interest. A total of 20 scalar-IMs and 21 vector-IMs representative of various characteristics of seismic loading were evaluated as candidate IMs. The criteria for identifying optimal IMs include consideration for the efficiency, sufficiency, and predictability of the given IMs. An error propagation approach was employed to evalute the overall uncertainty of EDPs under scenario earthquakes using different IMs as predictor variables. Based on the results of extensive comparative analyses, acceleration spectrum intensity (ASI), and the vector of peak ground acceleration and spectral acceleration at 0.3 s (peak ground acceleration (PGA) and Sa(0.3 s), respectively) are identified as the optimal scalar- and vector-IM for liquefaction triggering evaluation, respectively. However, Arias intensity (I_a) and vectors of [I_a, cumulative absolute velocity] and [PGA, I_a] are identified as the optimal scalar- and vector-IM for predicting the liquefaction-induced lateral displacements. The optimal IMs identified could be used in performance-based liquefaction hazard evaluations, to assess the liquefaction triggering and consequence of liquefiable sites.