Viscoelastic fault-based model of crustal deformation for the 2023 update to the US National Seismic Hazard Model

Fred F. Pollitz

Published September 11, 2022, SCEC Contribution #12350, 2022 SCEC Annual Meeting Poster #076

The 2023 update to the National Seismic Hazard (NSHM) model is informed by several deformation models that furnish geodetically estimated fault slip rates. Here I describe a fault-based model that permits estimation of long-term slip rates on discrete faults and the distribution of off-fault moment release. It is based on quantification of the earthquake cycle on a viscoelastic model of the seismogenic upper crust and ductile lower crust and mantle. I apply it to a large dataset of horizontal and vertical GPS interseismic velocities in the Western US, resulting in long-term slip rates on more than 1000 active faults defined for the NSHM. A reasonable fit to the GPS dataset is achieved with a set of slip rates designed to lie strictly within a-priori geologic slip rate bounds. Time-dependent effects implemented via a `ghost transient' have a profound effect on slip rate estimation and tend to raise slip rates along the Northern and Southern San Andreas fault by up to several mm/yr.

Key Words
Deformation GPS Interseismic

Citation
Pollitz, F. F. (2022, 09). Viscoelastic fault-based model of crustal deformation for the 2023 update to the US National Seismic Hazard Model. Poster Presentation at 2022 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy