Trimming a hazard logic tree with a new model-order-reduction technique

Earthquake Spectra
By: , and 



The size of the logic tree within the Uniform California Earthquake Rupture Forecast Version 3, Time-Dependent (UCERF3-TD) model can challenge risk analyses of large portfolios. An insurer or catastrophe risk modeler concerned with losses to a California portfolio might have to evaluate a portfolio 57,600 times to estimate risk in light of the hazard possibility space. Which branches of the logic tree matter most, and which can one ignore? We employed two model-order-reduction techniques to simplify the model. We sought a subset of parameters that must vary, and the specific fixed values for the remaining parameters, to produce approximately the same loss distribution as the original model. The techniques are (1) a tornado-diagram approach we employed previously for UCERF2, and (2) an apparently novel probabilistic sensitivity approach that seems better suited to functions of nominal random variables. The new approach produces a reduced-order model with only 60 of the original 57,600 leaves. One can use the results to reduce computational effort in loss analyses by orders of magnitude.

Publication type Article
Publication Subtype Journal Article
Title Trimming a hazard logic tree with a new model-order-reduction technique
Series title Earthquake Spectra
DOI 10.1193/092616EQS158M
Volume 33
Issue 3
Year Published 2017
Language English
Publisher Earthquake Engineering Research Institute
Contributing office(s) Geologic Hazards Science Center
Description 18 p.
First page 857
Last page 874
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