Estimates of the expected ground motion are essential for the design, assessment and decommissioning of offshore critical infrastructure. The North Sea is an area of moderate seismic hazard that contains many high-value offshore structures (e.g. oil, gas and wind-turbine facilities). The most recent seismic hazard assessment for the North Sea is about 20 years old, before many innovations in ground-motion modelling were developed. In this study, firstly we investigate which ground-motion model from more than a dozen recent models is the most appropriate for this area based on a residual analysis of ground-motion data from onshore seismic stations surrounding the North Sea. The limited data that are available for this area and the poor magnitude and distance coverage are inherent weaknesses of this residual analysis. A recent model developed for Europe and the Middle East is the model that shows the lowest bias and minimal statistical trends with respect to magnitude and distance. Following this, we develop adjustments to this best-performing model to relax the ergodic assumption, i.e. to make the model more site- and path-specific thereby allowing a smaller aleatory variability (sigma) to be used within a probabilistic seismic hazard assessment. The use of this adjusted model within seismic hazard assessments for the North Sea should lead to better estimates of the expected ground motion for critical offshore infrastructure sites, although this would require the effects of the geotechnical properties of the seafloor to be accounted for.

中文翻译：

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改善北海地震地面运动的预测

预期地面运动的估算对于海上关键基础设施的设计，评估和退役至关重要。北海是一个中等地震危险区，其中包含许多高价值的海上结构（例如，石油，天然气和风力涡轮机设施）。在开发地面运动模型的许多创新之前，对北海的最新地震灾害评估大约有20年的历史了。在这项研究中，首先，我们根据对北海周围陆上地震台站地面运动数据的残差分析，研究了十几种最新模型中哪种模式最适合该地区。可用于该区域的数据有限，幅值和距离覆盖率很差，是这种残留分析的固有弱点。针对欧洲和中东开发的最新模型是这样一种模型，该模型显示出关于震级和距离的最小偏差和最小统计趋势。此后，我们对该性能最佳的模型进行了调整，以放宽遍历遍历的假设，即使模型更具针对地点和路径的特定性，从而允许在概率地​​震危险性评估中使用较小的偶然变异性（sigma）。在北海的地震危险性评估中使用这种调整后的模型应该可以更好地估计关键的海上基础设施工地的预期地面运动，尽管这将需要考虑海底岩土属性的影响。