GEOTECHNICAL EARTHQUAKE ENGINEERING FOR OFFSHORE STRUCTURES

The offshore design codes and site-specific seismic hazard studies provide the framework for the earthquake design of offshore structures. The modem offshore design guidelineS' recommend that two levels of ground motion intensity are considered in design: a- ground motion which has a reasonable likelihood of not being exceeded at the site during the platform lifetime, and a ground motion from a rare, intense earthquake. It is usually the latter which poses the challenging engineering and design problems, in particular with respect to the behaviour of the soil foundation. The paper focuses on the geotechnical aspects of earthquake analysis and design for offshore installations. These include evaluation of local soil response, soil-structure interaction, analysis procedures for pile-supported jackets and gravity base platforms, and accounting for the uncertainty in engineering soil parameters.