Abstract
Abstract. Coseismic surface faulting is a significant source of hazard for critical plants and distributive infrastructure; it may occur either on the principal fault or as distributed rupture on nearby faults. Hazard assessment for distributed faulting is based on empirical relations which, in the case of normal faults, were derived almost 15 years ago using a dataset of US earthquakes. We collected additional case histories worldwide, for a total of 21 earthquakes, and calculated the conditional probability of distributed faulting as a function of distance from the principal fault. We found no clear dependency on the magnitude nor the time of occurrence of the earthquakes, but our data consistently show a higher probability of rupture when compared with the scaling relations currently adopted in engineering practice. We derive updated empirical regressions and show that the results are strongly conditioned by the averaging of earthquakes effectively generating distributed faulting at a given distance and those which did not generate faulting; thus, we introduce a more conservative scenario that can be included in a logic tree approach to consider the full spectrum of potential ruptures. Our results can be applied in the framework of probabilistic assessment of fault displacement hazard.
Highlights
Surface faulting is a significant source of hazard following moderate to strong earthquakes (i.e., M > ca. 6)
A probabilistic approach (i.e., PFDHA – probabilistic fault displacement hazard analysis) is the suggested method to calculate the expected displacement due to surface faulting for siting nuclear power plants and critical facilities (e.g., ANSI/ANS-2.30, 2015)
We initially computed the conditional probability of distributed faulting for each single event; we explored the role of magnitude and year of occurrence as factors affecting this value
Summary
Surface faulting is a significant source of hazard following moderate to strong earthquakes (i.e., M > ca. 6). The avoidance criterion is usually applied for mitigating fault displacement hazard when a fault strand’s location is certain; there are situations where crossing an active fault cannot be avoided (e.g., distributive infrastructure, pipelines). A probabilistic approach (i.e., PFDHA – probabilistic fault displacement hazard analysis) is the suggested method to calculate the expected displacement due to surface faulting for siting nuclear power plants and critical facilities (e.g., ANSI/ANS-2.30, 2015). This approach was firstly proposed by Youngs et al (2003) for the high-level nuclear waste repository in the Yucca Mountain, Nevada. The method is directly derived from probabilistic seismic hazard analysis (PSHA), firstly developed by Cornell (1968), which determines the annual rate of earthquakes in which a ground motion parameter exceeds a specific value, at a given location
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