2D site response modeling of the Treasure Island vertical array considering spatially varying input motions with non-vertical incidence

This study evaluates the impact of non-vertical incidence and spatially variable ground motions on seismic site response analyses by developing detailed two-dimensional finite element models of the Treasure Island site in San Francisco Bay, California. Site response analysis models often fail to capture all of the complexities of real-world seismic wave propagation, leading to discrepancies between theoretical and empirical transfer functions. By introducing models that account for non-vertical incidence and spatially variable ground motion due to path scattering, this study explores how these factors influence the results of the site response models. The findings indicate that considering non-vertical incidence and spatially variable input ground motions captures certain aspects of the inherent variability in empirical transfer functions, particularly in the fundamental frequency range, though the improvement on the mean prediction is marginal for this site. It is also found that the model predictions change based on the direction that waves are assumed to enter the model domain, suggesting that the alignment of incoming wave fields with site stratigraphy is an important factor for site response. • Non-vertical and spatially-variable input motion considered in 2D site response. • 2D finite element models are developed for Treasure Island downhole array site. • The studied features did not significantly affect 2D transfer functions at this site. • Alignment of subsurface stratigraphy and wave incidence angle found to be important. • SVGM introduces greater variability in the transfer functions at lower frequencies. • More variability in SVGM input affects greater change in mean transfer functions.