随着水下生产系统在中国深水油气田中的逐步应用，对于各种极端工况的分析也越来越详细，并应用在水下生产系统设计分析中。目前国内的水下生产系统设计处于起步阶段,在分析地震对水下生产系统的影响时，一般仅将地震等效载荷施加于结构上用以分析结构的承载能力和安全性，很少考虑地震对土壤的影响。为此，分析了地震循环剪应力作用下发生土壤液化的风险以及地震后土壤强度衰减引起的沉降量问题，并通过实际工程的计算分析证明了考虑地震作用下土壤液化分析和强度衰减分析的重要性。

With the subsea production system applied more and more widely in China deepwater oil and gas fields, various kinds of extreme conditions are analyzed and applied in the subsea design. Subsea production system design in China is still in the initial stage. When seismic influence is analyzed and designed, equivalent loads are imposed merely for calculating the bearing capacity and safety, which cannot analyze the impact of seismic load to soil foundation. Aiming at this problem, the soil liquefaction and the settlement induced by strength degradation under seismically induced cyclic shear stress are analyzed. From the calculation result of a subsea project, it can be seen that analysis on soil liquefaction and strength degradation has important significance.