Quantifying the Effects of Ground-Motion Duration on Seismic Slope Displacement Analyses for Subduction Zone Earthquakes

Abstract Seismic slope displacement analyses are crucial for assessing the performance of earth systems and natural slopes under earthquake loading. Input ground motions are important components of such analyses and represent one of the main sources of variability in estimated values of slope displacement. Most studies on seismic slope displacement analyses have been conducted using shallow crustal earthquake motions. However, ground motions from subduction zones are known to have comparatively longer durations. This study proposes a framework to quantify the effects of ground-motion duration on slope displacements using short- and long-duration ground-motion suites from subduction zone earthquakes. Challenges in isolating duration effects from those associated with the amplitude and frequency content of ground motions are overcome by creating sets of ground motions with the same amplitude and similar spectral shape, but with different significant durations. These equivalent short- and long-duration suites of motions are then utilized in nonlinear finite-element analyses to evaluate their impact on slope displacement. The finite-element model is developed to numerically simulate the strength and stiffness degradation of soils under cyclic loading from strong ground shaking. We find that the long-duration motions in our dataset can cause larger permanent displacements compared to their short-duration counterparts (with similar spectral shape but different duration), especially at higher ground shaking intensity levels that can trigger nonlinear soil behavior. Comparisons with simplified analyses show that the simplified methods can result in biased estimates of permanent displacements from the long-duration motions in our study. This study provides a framework to develop ground motion sets that can enable more in-depth investigations of the role of duration on seismic slope displacements and the damage potential of ground motions, particularly from subduction events.