The United States Geological Survey (USGS) National Seismic Hazard Model (NSHM) is the scientific foundation of seismic design regulations in the United States and is regularly updated to consider the best available science and data. The 2018 update of the conterminous US NSHM includes major changes to the underlying ground motion models (GMMs). Most of the changes are motivated by the new multi-period response spectra requirements of seismic design regulations that use hazard results for 22 spectral periods and 8 site classes. In the central and eastern United States (CEUS), the 2018 NSHM incorporates 31 new GMMs for hard-rock site conditions $(V_{S30}=3000\mathrm{m}/\mathrm{s})$, including the Next Generation Attenuation (NGA)-East GMMs. New aleatory variability and site-effect models, both specific to the CEUS, are applied to all median hard-rock GMMs. This article documents the changes to the USGS GMM selection criteria and provides details on the new CEUS GMMs used in the 2018 NSHM update. The median GMMs, their weights, epistemic uncertainty, and aleatory variability are compared with those considered in prior NSHMs. This article further provides implementation details on the CEUS site-effect model, which allows conversion of hard-rock ground motions to other site conditions in the CEUS for the first time in NSHMs. Compared with the 2014 NSHM hard-rock ground motions, the weighted average of median GMMs increases for large magnitude events at middle to large distance range, epistemic uncertainty increases in almost all situations, but aleatory variability is not significantly different. Finally, the total effect on hazard is demonstrated for an assumed earthquake source model in the CEUS, which shows an increased ring of ground motions in the vicinity of the New Madrid seismic zone and decreased ground motions near the East Tennessee seismic zone.

美国地质调查局（USGS）国家地震危险模型（NSHM）是美国地震设计法规的科学基础，并定期进行更新以考虑最佳的可用科学和数据。美国本土NSHM的2018年更新包括对基础地面运动模型（GMM）的重大更改。大部分更改是由地震设计法规新的多周期响应频谱要求引起的，该要求使用22个频谱周期和8个站点类别的危害结果。在美国中部和东部（CEUS），2018 NSHM纳入了针对硬岩场地条件的31种新GMM$（{\mathrm{伏特}}_{\mathrm{小号}30}=3000\mathrm{米}/\mathrm{s}）$，包括下一代衰减（NGA）-东GMM。CEUS特有的新的偶然性变异性和位点效应模型都适用于所有中位数硬岩GMM。本文记录了对USGS GMM选择标准的更改，并提供了2018 NSHM更新中使用的新CEUS GMM的详细信息。将中位GMM，其权重，认知不确定性和偶然性差异与先前NSHM中考虑的那些进行了比较。本文进一步提供了关于CEUS场地效应模型的实现细节，该模型允许在NSHM中首次将硬岩地面运动转换为CEUS中其他场地条件。与2014年NSHM硬岩地震动相比，中到远距离范围内大事件的中值GMM的加权平均值有所增加，几乎在所有情况下，认知不确定性都会增加，但偶然变异性没有显着差异。最后，在CEUS中假定的震源模型中证明了对灾害的总体影响，该模型表明新马德里地震带附近的地震动环增加，而东田纳西地震带附近的地震动环减少。