The 2023 Alaska National Seismic Hazard Model: Hazard Implications
Description:
The 2023 U.S. Geological Survey (USGS) National Seismic Hazard Model (NSHM) for the State of Alaska incorporates more than fifteen years of new data in updates to the earthquake rupture forecast (ERF) and ground motion model (GMM) components of the model. These changes result in large increases in predicted ground motions compared to the previous model published in 2007. The ERF incorporates an expanded crustal fault inventory, updated geologic and geodetic rate models, and several new source zones in key areas (e.g., Cook Inlet and the Coast Shear Zone). Crustal and subduction gridded seismicity models, based on an updated earthquake catalog that includes events through 2020, incorporate multiple catalog declustering and spatial smoothing methods. The Alaska-Aleutian arc geometry from Slab 2 is used to model depths for intraslab and small-magnitude (<M7) interface sources as well as the large-magnitude subduction interface geometry. The large-magnitude interface model also uses updated megathrust segmentation models and multiple earthquake rate models. The 2023 NSHM for Alaska uses the NGA-West 2 GMMs for crustal sources, NGA-Subduction global models for subduction interface sources, and NGA-Subduction Alaska regional models for subduction intraslab sources. Details of the updates to the ERF and GMM components have been presented elsewhere; here we focus on how key model updates lead to significant increases of more than a factor of two, in some areas, in earthquake hazard across south-central Alaska. For example, the updated interface rupture rates and the adoption of NGA-Subduction GMMs both lead to higher hazard across much of the Alaska-Aleutian arc. We show stepwise ratio and difference maps that illustrate the relative contributions to changes in hazard arising from each update to the ERF and GMM model components.
Session: The 2023 USGS National Seismic Hazard Model and Beyond [Poster Session]
Type: Poster
Date: 5/1/2024
Presentation Time: 08:00 AM (local time)
Presenting Author: Jason
Student Presenter: No
Invited Presentation:
Authors
Jason Altekruse Presenting Author Corresponding Author jaltekruse@usgs.gov U.S. Geological Survey |
Peter Powers pmpowers@usgs.gov U.S. Geological Survey |
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The 2023 Alaska National Seismic Hazard Model: Hazard Implications
Session
The 2023 USGS National Seismic Hazard Model and Beyond