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From research to practice in nonlinear site response: Observations and simulations in the Los Angeles basin

Domniki Asimaki, Wei Li, Jamison H. Steidl, & Jan Schmedes

Published 2007, SCEC Contribution #1047

There exists nowadays agreement between the earthquake engineering and seismological community that the assessment of local site effects is of great significance, both for mitigating seismic hazard and for performing detailed analyses of earthquake source characteristics. Nonetheless, there still exists large degree of uncertainty concerning the site categorization scheme to be used for quantifying the susceptibility of soil profiles to nonlinear effects, the mathematical model to be employed for the computationally efficient evaluation of these effects, and the site investigation program to ensure cost-effective predictions given the target level of design sophistication. Despite the fact that seismic observations of site response can provide critical constraints on interpretation methods for surface observations, the lack of a statistically significant number of in-situ strong motion records prohibits statistical analyses to be conducted and uncertainties to be quantified based entirely on field data. For this purpose, we here combine downhole observations and broadband ground motion synthetics in the Los Angeles Basin and present preliminary results of a comprehensive parametric study, which focuses on investigating the variability in ground-motion estimation introduced by nonlinear site-response methodologies and their associated input parameters. In particular, we address the uncertainty introduced in the assessment of seismic hazard by the selected site-specific ground motion analysis methodology, low-strain velocity and attenuation profiles of the near-surface and the deeper sediment structure, dynamic soil properties and nonlinear constitutive model input parameters. The long-term goal of this work is the establishment of a cost-effective and computationally-efficient framework for site parameterization and nonlinear site response simulation.

Asimaki, D., Li, W., Steidl, J. H., & Schmedes, J. (2007). From research to practice in nonlinear site response: Observations and simulations in the Los Angeles basin. Presentation at 4th International Conference on Earthquake Geotechnical Engineering.