The UCERF3 grand inversion: Solving for the long‐term rate of ruptures in a fault system

Bulletin of the Seismological Society of America
By: , and 

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Abstract

We present implementation details, testing, and results from a new inversion‐based methodology, known colloquially as the “grand inversion,” developed for the Uniform California Earthquake Rupture Forecast (UCERF3). We employ a parallel simulated annealing algorithm to solve for the long‐term rate of all ruptures that extend through the seismogenic thickness on major mapped faults in California while simultaneously satisfying available slip‐rate, paleoseismic event‐rate, and magnitude‐distribution constraints. The inversion methodology enables the relaxation of fault segmentation and allows for the incorporation of multifault ruptures, which are needed to remove magnitude‐distribution misfits that were present in the previous model, UCERF2. The grand inversion is more objective than past methodologies, as it eliminates the need to prescriptively assign rupture rates. It also provides a means to easily update the model as new data become available. In addition to UCERF3 model results, we present verification of the grand inversion, including sensitivity tests, tuning of equation set weights, convergence metrics, and a synthetic test. These tests demonstrate that while individual rupture rates are poorly resolved by the data, integrated quantities such as magnitude–frequency distributions and, most importantly, hazard metrics, are much more robust.

Publication type Article
Publication Subtype Journal Article
Title The UCERF3 grand inversion: Solving for the long‐term rate of ruptures in a fault system
Series title Bulletin of the Seismological Society of America
DOI 10.1785/0120130180
Volume 104
Issue 3
Year Published 2014
Language English
Publisher Seismological Society of America
Contributing office(s) Earthquake Science Center
Description 24 p.
First page 1181
Last page 1204
Online Only (Y/N) N
Additional Online Files (Y/N) N
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