This study presents the probabilistic seismic hazard assessment (PSHA) for a nuclear site in the UK, Wylfa Newydd. The PSHA was defined at a bedrock horizon with shear wave velocity of 3000 m/s and developed to capture the centre, body and range of the technical defensible interpretations. Although not a formal SSHAC (Senior Seismic Hazard Assessment Committee) process, the PSHA met all the SSHAC Level 2 requirements with some aspects of SSHAC Level 3 and 4. Two base source models were developed: SM1 mainly driven by the observed seismicity and SM2 guided by the geology and tectonics. To capture epistemic uncertainty, variations of boundaries were included in the logic tree, resulting in five different models. Based on the selection discussed by Villani et al. (Bull Seismol Soc Am 109(4):1378–1400, 2019), four empirical models adjusted to the hard rock site conditions of Wylfa Newydd and a site-specific stochastic GMPE, developed within this project, were adopted in the logic tree for the median prediction. For all GMPEs a logic tree for the single-station sigma model was adopted. The PSHA resulted in a mean peak ground acceleration value for annual probability of exceedance of 10⁻⁴ of 0.192 g. The comparison of the mean 10⁻⁴ uniform hazard spectrum with the traditional piecewise linear design spectrum showed significant conservatism up to 20 Hz and underestimation at higher frequencies. To overcome this limitation, a performance-based design spectrum, following US practice (ASCE/SEI 43-05), was therefore recommended; this marks a significant difference to the traditional UK design practice.

中文翻译：

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英国新核电站Wylfa Newydd的概率地震灾害评估

这项研究提出了英国Wylfa Newydd核电站的概率地震危险性评估（PSHA）。PSHA被定义在基岩层，剪切波速度为3000 m / s，并被开发以捕获技术辩解的中心，主体和范围。尽管不是正式的SSHAC（高级地震危险性评估委员会）流程，但PSHA满足了SSHAC 3级和4级某些方面的所有SSHAC 2级要求。开发了两个基本源模型：主要由观察到的地震活动驱动的SM1和由SM2指导的SM2由地质和构造学。为了捕获认知不确定性，逻辑树中包括了边界的变化，从而产生了五个不同的模型。根据Villani等人讨论的选择。（Bull Seismol Soc Am 109（4）：1378–1400，2019），在该项目中开发的四个根据Wylfa Newydd硬岩场地条件调整的经验模型和特定于现场的随机GMPE在逻辑树中用于中位数预测。对于所有GMPE，均采用了单站sigma模型的逻辑树。PSHA得出的平均地面加速度峰值为每年超过10的概率-1.92的^-4。平均10 ^-4均匀危险谱与传统分段线性设计谱的比较显示，高达20 Hz的显着保守性和较高频率下的低估。为克服此限制，因此建议遵循美国惯例（ASCE / SEI 43-05）基于性能的设计范围；这标志着与传统的英国设计实践有很大的不同。