A Simulation Platform to Quantify the Effects of Spatial Variability in Site Response for PSHA

Session: Near-Surface Effects: Advances in Site Response Estimation and Its Applications
Type: Oral
Date: 4/28/2020
Time: 02:45 PM
Room: 110 + 140
Description: 

Physics-based ground motion models have long explored the variability of ground surface motion associated with material and geometric heterogeneities of the subsurface. Probabilistic seismic hazard practice, however, still relies on integrating aleatory variability associated with site response analyses (via hybrid or fully-probabilistic methods) as well as epistemic uncertainty associated with sparse spatial measurements by randomizing one-dimensional (1D) soil profiles. It has been recently shown that this idealization may be a poor predictor of site response variability at sites with strong subsurface relief and strongly heterogeneous layers with large coefficients of variation of intra-layer properties. Furthermore, at most sites, incorporating variability in this manner reduces the mean site amplification as the variability increases, especially in the high frequency regime. In this paper, we present an open source computer code that renders the site response computation of two-dimensional (2D) randomized profiles computationally tractable for engineering design applications. We present examples where 2D realizations yield statistical properties of ground surface motions that substantially differ from what would result from 1D soil profile randomization; and we comment on future implications of integrating 2D site response at rock sites with spatial variability, where the effects of scattering are still interpreted via 1D site response through the prism of high-frequency attenuation, such as damping or the site attenuation parameter k₀.

Presenting Author: Domniki Asimaki

Authors