Evaluation of a Non-Linear Deformation Analysis Method Usingthe Jensen Filtration Site-Northridge Earthquake Case History

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9416247 Moriwaki The Joseph Jensen Filtration Plant (JFP) in the San Fernando Valley, California, provides an unprecedented case history of seismically induced permanent ground deformations. The site has been strongly shaken by two earthquakes-the 1971 San Fernando earthquake and the 1994 Northridge earthquake. These two earthquakes produced large permanent ground deformations and ground cracks at parts of the site. The site was thoroughly investigated and studied following the San Fernando earthquake, leading to a conclusion that the loose alluvium underlying the fill (up to 50 ft thick) at the site probably liquefied and contributed to the permanent ground deformations. In 1988, the owner and operator of the plant, the Metropolitan Water District of Southern California (Metropolitan), contracted a thorough geotechnical and seismic investigation of the site prior to a major expansion of the facility. Following the 1994 earthquake, Woodward-Clyde has been working with the Metropolitan to map the permanent ground deformations, ground cracks, and other damage at the site. The project involves the following: an assessment of the site conditions; the development of free-field ground motions at the site corresponding to the 1994 earthquake; and the documentation, simplified analyses, and nonlinear numerical analyses of permanent ground deformations at the site due to the 1971 and 1994 earthquakes. The documentation, comparison, and evaluation of the permanent ground deformations at the JFP site during these two earthquakes not only provides a unique and important case history of ground failure, but also provides an opportunity to evaluate the use of nonlinear numerical modeling of the ground deformation as a practical and reliable design tool. Evaluations with conventional and empirical methods also serve to provide a common basis for comparison. ***