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Risk-targeted alternatives to deterministic ground motion caps in U.S. seismic provisions
Earthquake Spectra ( IF 5 ) Pub Date : 2020-02-25 , DOI: 10.1177/8755293019892010
Jonathan P Stewart 1 , Nicolas Luco 2 , John D Hooper 3 , C B Crouse 4
Affiliation  

Since their inception over 20 years ago, the maximum considered earthquake ground motion maps in U.S. building codes have capped probabilistic values with deterministic ground motions from characteristic earthquakes on known active faults. This practice has increasingly been called into question both because of spatially non-uniform risk levels that are produced (risk being higher mainly in coastal California) and practical difficulties in defining characteristic earthquakes from recent earthquake rupture forecast models. We describe two proposals developed to enable phase-out of deterministic caps. One approach modestly increases collapse risk targets nationwide based on recent information on return periods of characteristic earthquakes on major central and eastern U.S. seismic sources; adoption of this approach would remove the perceived need for caps in California. The second approach uses geographically varying collapse risk targets, being higher near the highly active faults in California and unchanged elsewhere. Neither approach was adopted for the 2020 National Earthquake Hazards Reduction Program recommended seismic Provisions for new building structures, but they are described in a Part 3 document to accompany the Provisions and Commentary.

中文翻译:

美国地震规定中确定性地震动上限的风险目标替代方案

自 20 多年前推出以来,美国建筑规范中考虑的最大地震地面运动地图已经用已知活动断层上的特征地震的确定性地面运动来限制概率值。由于所产生的空间风险水平不均匀(风险主要在加利福尼亚沿海地区较高)以及根据最近的地震破裂预测模型定义特征地震的实际困难,这种做法越来越受到质疑。我们描述了为逐步淘汰确定性上限而开发的两个提案。一种方法是根据美国中部和东部主要震源特征地震重现期的最新信息,在全国范围内适度提高倒塌风险目标;采用这种方法将消除加利福尼亚对上限的感知需求。第二种方法使用地理上不同的崩塌风险目标,在加利福尼亚高度活跃的断层附近更高,而在其他地方保持不变。2020 年国家减少地震灾害计划为新建筑结构推荐的抗震规定均未采用这两种方法,但在规定和评论随附的第 3 部分文件中对其进行了描述。
更新日期:2020-02-25
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