Ports of Los Angeles and Long Beach Port-Wide Ground Motion Study

The Port of Los Angeles (POLA) and Port of Long Beach (POLB) jointly embarked on a ground motion study of the Los Angeles-Long Beach harbor area to develop consistent seismic ground motion recommendations for design of structures within the ports. Regional and site geology and seismicity were reviewed to establish the latest understanding on geological features and faults contributing to the seismic hazard at the POLA and POLB, with particular attention on the Palos Verdes fault, a major fault in the region that passes directly through the POLA area, and the nearby Newport-Inglewood fault. Ground conditions affecting site response were interpreted from borehole and geophysical data available in existing geotechnical reports for both ports. Probabilistic seismic hazard analyses were performed using latest revisions of ground-attenuation models commonly used in California, including the latest version of an attenuation model that is being developed as part of the Pacific Earthquake Engineering Research/Lifelines Next Generation Attenuation Project. Adjustments for near-fault rupturing effects were made and uncertainties in earthquake source and attenuation model parameters were addressed through the use of logic trees. Local site conditions were incorporated based on quantitative and qualitative assessment and supported by empirical strong motion data. Horizontal and vertical-component uniform hazard spectra for design events were developed for various damping values and seven sets of spectrum-compatible acceleration-time histories were also developed.