Evaluation of Site Response for Deepwater Field

The move of the offshore industry into ever greater water depths presents significant challenges for geotechnical and seismic engineering. Soil conditions at deepwater sites are well outside the range of typical onshore experience. Given the very low strength soils, earthquake loads often control foundation design. In these conditions the evaluation of seismic design criteria is critical to project success. This paper discusses the site response analysis for a field in 650 m water depth offshore the Nile Delta. Soil amplification predicted using the SHAKE type equivalent linear analyses is compared to a non-linear approach. The equivalent linear approach is seen to predict significantly larger spectral acceleration than the non-linear analysis for these soil conditions. Implications for seismic design criteria are discussed.