Application of Single-Station Sigma and Site-Response Characterization in a Probabilistic Seismic-Hazard Analysis for a New Nuclear Site

Abstract

Aleatory variability in ground-motion prediction, represented by the standard deviation (sigma) of a ground-motion prediction equation, exerts a very strong influence on the results of probabilistic seismic-hazard analysis (PSHA). This is especially so at the low annual exceedance frequencies considered for nuclear facilities; in these cases, even small reductions in sigma can have a marked effect on the hazard estimates. Proper separation and quantification of aleatory variability and epistemic uncertainty can lead to defensible reductions in sigma. One such approach is the single-station sigma concept, which removes that part of sigma corresponding to repeatable site-specific effects. However, the site-to-site component must then be constrained by site-specific measurements or else modeled as epistemic uncertainty and incorporated into the modeling of site effects. The practical application of the single-station sigma concept, including the characterization of the dynamic properties of the site and the incorporation of site-response effects into the hazard calculations, is illustrated for a PSHA conducted at a rock site under consideration for the potential construction of a nuclear power plant.

The effect of alternative seismotectonic models on PSHA results – a sensitivity study for two sites in Israel

“…6, partitioning the Arava and Jericho faults into three segments each. This segmentation is mainly based on the map of active faults published by the Geological Survey of Israel (Sagy et al, 2013) as well as on the work of Sadeh et al (2012). The continuous model does not ignore geometrical segmentation of the DST but rather assumes the likelihood of multi-segment ruptures.…”

“…Table 2 lists the different fault segments in our analysis and their respective lengths. In the Dead Sea basin itself, Sadeh et al (2012) suggest two faults on both sides of the basineastern and western. In order to maintain the correct moment balance in the segmented model (i.e.…”

“…Uncertainties are propagated throughout the analysis and have been shown to dominate the results for highrisk projects, such as NPPs, hydraulic dams, and major lifelines (e.g. Rodriguez-Marek et al, 2014). It is common to describe uncertainty as either aleatory or epistemic (e.g.…”

Single Station Sigma for Turkish Strong Motion Stations

“…[3][4][5]. Over the last decade, the availability of recorded ground motions at single sites caused by multiple earthquakes originating from the same tectonic sources has allowed researchers to estimate what is referred to as nonergodic standard deviation (also referred to as single station standard deviation or single station sigma) of ground motion [6][7][8][9][10][11][12][13]. These studies illustrated in general that average nonergodic standard deviations are lower than their ergodic equivalents.…”

“…Hence computing nonergodic standard deviation, that offers more realistic quantification of ground motion variability at a specific site has become particularly important in the evaluation of ground motions utilized for the design of critical facilities especially such as nuclear power plants [11,[15][16]. The focus of this study is to compute nonergodic standard deviation based on the Turkish strong motion database and determine the effect of using it instead of ergodic standard deviation on seismic hazard estimates for the Fatih-Kadikoy districts of Istanbul.…”