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Analyses and Implications of Deformation Models of the U.S. National Seismic Hazard Model 2023

Description: 

Five deformation models were developed as potential inputs for the 2023 update of the National Seismic Hazard Model (NSHM). Four of these models rely on GNSS velocity data as primary constraints (the “Zeng,” ShenBird,” “Pollitz,” and “Evans” models), and one relies on published geologic slip rate information as the primary constraints (“geologic”). The five-model suite seeks to characterize the range of epistemic uncertainties on deformation rates across the western U.S. Given that all five models have different governing assumptions and modeling choices, there is significant variability of on-fault slip rates within the suite for many faults. This variability within the suite presents a conundrum: which deformation model rate is the “right” value for seismic hazard analysis? Here, we present an outlier analysis of the five-model suite, discuss the influence of deformation model assumptions within the fault system solution (inversion) framework, and highlight implications of different branch weight options on hazard metrics. We find that the Evans and Pollitz models account for the most variability within the five-model suite, with these models supplying rates ~5x greater or less than the median rate. In contrast, the Zeng, ShenBird, and geologic models provide the median rate for ~85% of all faults. We show that branch weights for deformation models can locally impact peak ground acceleration (2% in 50 year) by a factor of ~2. Refining existing deformation models, including testing alternative assumptions within each model to provide null space exploration, will be key for defining epistemic uncertainties in future fault system solutions.

Session: USGS National Seismic Hazard Models: 2023 and Beyond [Poster]

Type: Poster

Date: 4/18/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Alexandra E. Hatem

Student Presenter: No

Invited Presentation: 

Authors