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Early Results From Deformation Models of the Western US for the 2023 Update to the US National Seismic Hazard Model

We describe geodetic and geologic information assembled for the 2023 update to the National Seismic Hazard Model (NSHM), a set of deformation models to interpret these data and implications for earthquake rates in the Western US. Recent updates provide much larger datasets of GNSS crustal velocities than used in the 2014 NSHM, as well as hundreds of new faults considered as active sources for the current NSHM. These data are interpreted by four quantitative models of deformation which estimate fault slip rates and their uncertainties together with off-fault moment release rates. Key innovations in the current NSHM relative to past practice include: (1) the addition of two new (in addition to two existing) deformation models, (2) the inclusion of hundreds of additional (primarily very low slip rate) faults and the availability of more constraints on geologic slip rates, (3) accounting for fault creep through development of an independent creep-rate model whose results are incorporated into the deformation models and (4) accounting for time-dependent earthquake-cycle effects through development of viscoelastic models of the earthquake cycle along the San Andreas fault and the Cascadia subduction zone. The current deformation models provide a new assessment of discrepancies between geologic and geodetic slip rates, while at the same time highlighting the need for both geologic and geodetic slip rates to robustly inform the earthquake rate model.

Session: 50-State Update of the USGS National Seismic Hazard Models II

Type: Oral

Room: Regency E-G

Date: 4/20/2022

Presentation Time: 10:30 AM Pacific

Presenting Author: Fred F. Pollitz

Student Presenter: No

Additional Authors