Progress on understanding and modeling earthquake ground motions and site response in the central and eastern United States
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Oliver Boyd
USGS
- Date & Time
- Location
- Online-only seminar via Microsoft Teams
- Host
- Tara Nye
- Summary
Substantial progress has been made in understanding and modeling earthquake site response in the central and eastern United States over the last decade due in large part to the passage of USArray as well as the curiosity and dedication of many researchers. In this presentation, I will review these achievements, discuss how they’ve been applied to improve the U.S. Geological Survey National Seismic Hazard Model (NSHM), and showcase ongoing efforts. Similar to the use of Z1.0 and Z2.5 in western U.S. ground motion models, sediment thickness has been found to be a strong predictor of the frequency and spatial variability of ground motions in parts of the central and eastern United States. For application to the 2023 NSHM, a sediment thickness surface was constructed for the Atlantic and Gulf Coastal Plains, and multiple site amplification models were evaluated. Amplification models dependent on sediment thickness, site natural period, and source-to-site path length were compared with datasets of observed ground motions to evaluate the ability of the new models to improve ground motion estimates. These models can account for observed trends in sediment-thickness and period-dependent residuals, but some tuning is required. If implemented in the NSHM with full weight, these amplification models reduce predicted short-period (1 s) ground motions in the Coastal Plains appreciably. Ongoing efforts aim to better characterize subsurface seismic velocity, appreciate the effect of differences in regional geology, account for resonance effects, model 3D wave propagation, and incorporate widely reported felt intensities. I expect many improvements for the 2029 NSHM.