Profile extrema for visualizing and quantifying uncertainties on excursion regions. Application to coastal flooding

Azzimonti, Dario; Ginsbourger, David; Rohmer, Jérémy; Idier, Déborah (2019). Profile extrema for visualizing and quantifying uncertainties on excursion regions. Application to coastal flooding. Technometrics, 61(4), pp. 474-493. Taylor & Francis 10.1080/00401706.2018.1562987

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We consider the problem of describing excursion sets of a real-valued function f, that is, the set of inputs where f is above a fixed threshold. Such regions are hard to visualize if the input space dimension, d, is higher than 2. For a given projection matrix from the input space to a lower dimensional (usually 1, 2) subspace, we introduce profile sup (inf) functions that associate to each point in the projection’s image the sup (inf) of the function constrained over the pre-image of this point by the considered projection. Plots of profile extrema functions convey a simple, although intrinsically partial, visualization of the set. We consider expensive to evaluate functions where only a very limited number of evaluations, n, is available, for example, n<100d, and we surrogate f with a posterior quantity of a Gaussian process (GP) model. We first compute profile extrema functions for the posterior mean given n evaluations of f. We quantify the uncertainty on such estimates by studying the distribution of GP profile extrema with posterior quasi-realizations obtained from an approximating process. We control such approximation with a bound inherited from the Borell-TIS inequality. The technique is applied to analytical functions (d = 2, 3) and to a five-dimensional coastal flooding test case for a site located on the Atlantic French coast. Here f is a numerical model returning the area of flooded surface in the coastal region given some offshore conditions. Profile extrema functions allowed us to better understand which offshore conditions impact large flooding events.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Department of Mathematics and Statistics > Institute of Mathematical Statistics and Actuarial Science

UniBE Contributor:

Azzimonti, Dario Filippo and Ginsbourger, David

Subjects:

500 Science > 510 Mathematics
500 Science > 550 Earth sciences & geology

ISSN:

0040-1706

Publisher:

Taylor & Francis

Language:

English

Submitter:

David Ginsbourger

Date Deposited:

14 Jan 2020 09:14

Last Modified:

14 Jan 2020 09:14

Publisher DOI:

10.1080/00401706.2018.1562987

BORIS DOI:

10.7892/boris.125293

URI:

https://boris.unibe.ch/id/eprint/125293

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