Fault displacement hazard estimation at lifeline–fault crossings: A simplified approach for engineering applications

Abstract

Lifelines, such as pipelines, roads, and tunnels, are critical infrastructure and when crossing active tectonic faults, a reliable estimation of the fault displacement in case of an earthquake is required. The first and simplest approach is to use empirical fault scaling relations to compute the design fault displacement, but this may result in an unknown level of safety. Thus, the probabilistic fault displacement hazard analysis (PFDHA) is the appropriate tool to assess the fault displacement hazard within a performance-based framework. Based upon an established PFDHA model, we present a simplified approach for engineering applications focusing on the lifeline–fault crossing along with appropriate simplifications and assumptions to extend its applicability to numerous faults. The aim is to provide a structure-independent approach of PFDHA that can be used when a site-specific study is not required, not possible (e.g., absence of recent sediments for dating past events), or too cumbersome, e.g., for lifeline route selection. Additionally, an in-depth investigation is presented on the key parameters, such as maximum earthquake magnitude, fault length, recurrence rate of all earthquakes above a minimum magnitude, and lifeline-fault crossing site, and how they affect the hazard level. This approach will be the basis for deriving hazard-consistent expressions to approximate fault displacement for use within the Eurocodes. The latter is intended to serve as a compromise between hazard-agnostic fault scaling relations and a comprehensive PFDHA, which requires detailed calculations and site-specific seismological data.

Conservative Evaluation of Fault Displacement Hazard for a Nuclear Site in Case of Insufficient Data on the Fault Activity

“…In the proposed methodology, the probability of the surface scrap of the rupture intersecting the site is calculated, assuming the rupture can occur at any position within the mapped fault length with uniform probability. This is different from [26], where the calculation of the probability of surface scarp crossing the site for three typical configurations of the fault rupture scarp relative to the site are accounted for, depending on the three rupture lengths (short, medium, and long). The uniform distribution is a conservative assumption since the rupture is preferably in the fault's middle part; see [37].…”

“…Scaling Relation for SRL Weights Wells and Coppersmith (1994) [33] 0.5 Leonard (2014) [34] 0.25 Melissianos et al ( 2023) [26], 𝑆𝑅𝐿 ≈ 0.75 • 𝑅𝐿, RL by Wells and Coppersmith (1994) [33] 0.25…”

“…Other efforts have been made to develop simplified methods to evaluate fault displacement. In [25,26], a probabilistic fault displacement hazard evaluation methodology was developed for the fault crossing a lifeline.…”

“…Since the faults are accurately mapped, the uncertainty of the fault is neglected. For example, in [25,26], it is accounted for that the study fault crosses the site. However, contrary to [25,26], a uniform distribution of the rupture along the fault is assumed, and the dependence of the displacement on the relative position of the rupture to the site does not need to be considered.…”

“…For example, in [25,26], it is accounted for that the study fault crosses the site. However, contrary to [25,26], a uniform distribution of the rupture along the fault is assumed, and the dependence of the displacement on the relative position of the rupture to the site does not need to be considered. The total probability theorem in the study is used for the non-zero surface displacement and the mean annual probability of exceedance for average displacement.…”