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  • KrsTwnJnt_OcnEng_SptDpn_15022016

    Rights statement: This is the author’s version of a work that was accepted for publication in Ocean Engineering. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Ocean Engineering, 118, 2016 DOI: 10.1016/j.oceaneng.2016.04.013

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Assessing extremal dependence of North Sea storm severity

Research output: Contribution to journalJournal article

Published
<mark>Journal publication date</mark>15/05/2016
<mark>Journal</mark>Ocean Engineering
Volume118
Number of pages18
Pages (from-to)242-259
<mark>State</mark>Published
Early online date23/04/16
<mark>Original language</mark>English

Abstract

Extreme value theory provides asymptotically motivated methods for modelling the occurrences of extreme values of oceanographic variables, such as significant wave height at a single location. Problems are often multivariate or spatial in nature, where interest lies in the risk associated with joint occurrences of rare events, e.g. the risk to multiple offshore structures from a storm event. There are two different classes of joint tail behaviour that have very different implications: asymptotic independence suggesting that extreme events are unlikely to occur together, and asymptotic dependence implying that extreme events can occur simultaneously. It is vital to have good diagnostics to identify the appropriate dependence class. If variables are asymptotically independent, incorrectly assuming an asymptotically dependent model can lead to overestimation of the joint risk of extreme events, and hence to higher than necessary design costs of offshore structures. We develop improved diagnostics for differentiating between these two classes, which leads to increased confidence in model selection. Application to samples of North Sea sea-state and storm-peak significant wave height suggests that tail dependence changes with wave direction and distance between spatial locations, and that in most cases asymptotic independence seems to be the more appropriate assumption.

Bibliographic note

This is the author’s version of a work that was accepted for publication in Ocean Engineering. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Ocean Engineering, 118, 2016 DOI: 10.1016/j.oceaneng.2016.04.013