Seismic Response of Levees in the Sacramento-San Joaquin Delta

The seismic response of levees in the Sacramento-San Joaquin Delta, where the subsurface soils include thick deposits of highly organic soils, is evaluated. One-dimensional (1-D) and two-dimensional (2-D) equivalent-linear analyses were performed that accounted for variability in ground motions, dynamic properties, and soil profiles. Regression models were developed for: (1) the ratio of spectral accelerations at levee crests computed by 2-D versus 1-D response analyses, (2) stress reduction factors from 1-D site response analyses and seismic coefficient reduction factors for various failure surface depths from the 2-D response analyses, and (3) Newmark sliding block displacements computed for the input NEHRP site D ground motions and the computed seismic coefficient time series. The results of these regression models are compared to those obtained in previous studies involving different soil conditions, geometries, and motions. Newmark sliding block displacement hazard curves were calculated for a representative site in the Sacramento-San Joaquin Delta, and the contributions of various uncertainties to the displacement hazard curves are described.