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A New Ground Motion Model for Coastal Plain Region of the U.S Considering Sediment Thickness

This study aims to derive adjustment factors for the median of the NGA-East ground-motion models (GMMs) targeting the Gulf Coast and the Coastal Plain of the United States. Within the region collectively referred to as the Coastal Plain, we formulate a set of adjustment factors based on sediment thickness and rupture distance. This study uses sediment thickness contour maps from Boyd et al. (2024) and a comprehensive dataset to compute residuals by subtracting the natural logarithms of observed data from those predicted by the median of the NGA-East GMMs. This dataset merges the NGA-East dataset (Goulet et al., 2014), the Chapman and Guo (2021) dataset, and the newly compiled and verified USGS dataset (Thompson et al., 2023). A mixed-effects regression separates total residuals into between-event and within-event components. Adjustment factors for stations within the Coastal Plain are derived by regressing within-event residuals using a functional form incorporating sediment thickness and rupture distance. The results indicate that the proposed adjustment factors effectively mitigate residual trends related to site and path terms across most periods for stations within the Coastal Plain. These findings apply to seismic hazard and risk assessments for sites within the Coastal Plain.

Session: Accuracy and Variability of Physics-based Ground Motion Modeling [Poster]

Type: Poster

Room: Exhibit Hall

Date: 4/15/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Mehran Davatgari-Tafreshi

Student Presenter: No

Invited Presentation: 

Poster Number: 81

Additional Authors