37-18 Improving the geometric representation of faults in the U.S. National Seismic Hazard Model

Session: Geoscience Research Poster Showcase by 2YC and 4YCU Undergraduate Students

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The U.S. Geological Survey’s National Seismic Hazard Model (NSHM) calculates the frequency of earthquakes across the country to estimate potential ground shaking. Outputs of the model are used to establish insurance rates, building codes, and public safety planning. The most recent update, published in 2023 (NSHM23), significantly expanded the number of active faults in the model. However, the simple depiction of faults in NSHM23 does not fully capture the complexities of real fault surfaces and sub-surface geometries. The next update, planned for 2029 (NSHM29), aims to address this by representing faults as three-dimensional meshes that account for variations in seismogenic depth, local topography, fault intersections, and dip uncertainty. Preliminary NSHM29 fault meshes were developed from NSHM23 faults and subsurface information using PyVista. We calculated fault areas to understand how corrections for seismogenic depth, topography, and fault intersections during mesh creation impacts geologic moment rate, which directly influences earthquake frequency within the NSHM. Analysis of the results was completed using scatter plots and maps that depicted ratios and absolute changes in area and moment rate. This research reveals how different assumptions influence fault area and geologic moment rate to varying degrees. Some faults showed substantial changes in geologic moment rate from the combined effects of seismogenic depth, topography, and possible fault intersections, while others showed comparatively little. Our approach improves the geometric modeling of faults in the next iteration of NSHM by adding greater geometric fidelity to the fault model and is a step forward in probabilistic seismic hazard modeling. This work was conducted as part of the Geo-Launchpad internship program, supported by the National Science Foundation's National Geophysical Facility operated by EarthScope Consortium.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-19988

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