Extreme events: a framework for assessing natural hazards

摘要

The two-step framework for over-threshold modelling of environmental extremes proposed in Bernardara et al. (Nat Hazards Earth Syst Sci 14:635-647, 2014) for univariate analyses is generalized to an event-based framework applicable to multivariate analyses. The distinction between sequential values (temporal observations at a given time step) and the event-describing values (such as storm peaks in univariate Peaks-Over-Threshold extrapolations) is further detailed and justified. The classification of multivariate analyses introduced in Mazas and Hamm (Coast Eng 122:44-59, 2017) is refined and linked to the meaning of the concepts of event, sampling and return period that is thoroughly examined, their entanglement being highlighted. In particular, sampling is shown to be equivalent to event definition, identification and description. Event and return period definition are also discussed with respect to the source phenomena or to response (or structure) phenomena. The extreme event approach is thus proposed as a comprehensive framework for univariate and multivariate analyses for assessing natural hazards, seemingly applicable to any field of environmental studies.