Mignan, Arnaud

Integrating diverse expert opinions in hazard and risk projects is essential to managing subjective decisions and quantifying uncertainty to produce stable and trustworthy results. A structured procedure is necessary to organize the gathering of experts' opinions while ensuring transparency, accountability, and independence in judgements. We propose a novel Multiple-Expert management Protocol (MEP) to address this challenge, providing procedural guidelines for conducting single to multi-hazard risk analyses. MEP establishes a workflow to manage subjectivity rooted in (i) moderated and staged group interactions, (ii) trackable blind advice through written elicitations with mathematical aggregation, (iii) participatory independent review, (iv) close cooperation between scientific and managerial coordination, and (v) proper and comprehensive documentation. Originally developed for stress testing critical infrastructure, MEP is designed as a single, flexible, technology-neutral procedural workflow applicable to various sectors. Moreover, its scalability allows it to adapt from high to low-budget projects and from complex probabilistic multi-hazard risk assessments to standard single-hazard analyses, with different experts' degree and type of involvement depending on available funding and emerging controversies. We present two compelling case studies to showcase MEP's practical applicability: a multi-hazard risk analysis for a port infrastructure and a single-hazard regional tsunami hazard assessment.

Recent natural disasters that seriously affected critical infrastructure (CI) with significant socio-economic losses and impact revealed the need for the development of reliable meth- odologies for vulnerability and risk assessment. In this paper, a risk-based multi-level stress test method that has been recently proposed, aimed at enhancing procedures for evaluation of the risk of critical non-nuclear infrastructure systems against natural hazards, is speci- fied and applied to six key representative CIs in Europe, exposed to variant hazards. The following CIs are considered: an oil refinery and petrochemical plant in Milazzo, Italy, a conceptual alpine earth-fill dam in Switzerland, the Baku–Tbilisi–Ceyhan pipeline in Tur- key, part of the Gasunie national gas storage and distribution network in the Netherlands, the port infrastructure of Thessaloniki, Greece, and an industrial district in the region of Tuscany, Italy. The six case studies are presented following the workflow of the stress test framework comprised of four phases: pre-assessment phase, assessment phase, decision phase and report phase. First, the goals, the method, the time frame and the appropriate stress test level to apply are defined. Then, the stress test is performed at component and system levels and the outcomes are checked and compared to risk acceptance criteria. A stress test grade is assigned, and the global outcome is determined by employing a grading system. Finally, critical components and events and risk mitigation strategies are formu- lated and reported to stakeholders and authorities.

Making communities safer requires better tools to identify, quantify, and manage risks. Among the most important tools are stress tests, originally designed to test the risk posed by nuclear power plants. A complementary harmonized multilevel stress test for nonnuclear civil infrastructure systems against natural hazards is proposed. Each stress test level is characterized by a different scope and a different level of risk analysis complexity to suit different civil infrastructure systems, different hazards, and different risks. The stress test consists of the following phases. First, the goals and the methods for the risk analysis are defined. The test is then performed at the component and system levels, followed by a verification of the findings. A penalty system is defined to adjust the output of the risk assessment according to the limitations of the risk analysis methods used. The adjusted risk assessment results are then passed to a grading system to determine the outcome of the stress test. Finally, the risk assessment results are reported, and the stress test outcomes are communicated to stakeholders and authorities.

The effective management of the risks posed by natural and man-made hazards requires all relevant threats and their interactions to be considered. This paper proposes a three-level framework for multi-risk assessment that accounts for possible hazard and risk interactions. The first level is a flow chart that guides the user in deciding whether a multi-hazard and risk approach is required. The second level is a semi-quantitative approach to explore if a more detailed, quantitative assessment is needed. The third level is a detailed quantitative multi-risk analysis based on Bayesian networks. Examples that demonstrate the application of the method are presented.

The Non-Critical Precursory Accelerating Seismicity Theory (PAST) has been proposed recently to explain the formation of accelerating seismicity (increase of the a-value) observed before large earthquakes. In particular, it predicts that precursory accelerating seismicity should occur in the same spatiotemporal window as quiescence. In this first combined study we start by determining the spatiotemporal extent of quiescence observed prior to the 1997Mw= 6Umbria-Marche earthquake, Italy, using the RTL (Region-Time-Length) algorithm. We then show that background events located in that spatiotemporal window form a clear acceleration, as expected by the Non-Critical PAST. This result is a step forward in the understanding of precursory seismicity by relating two of the principal patterns that can precede large earthquakes.