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City-scale Assessment of Site and Basin Effects in Selected CEUS Sedimentary Basins: Memphis and New York City

Description: 

Many cities in the central and eastern United States (CEUS) are located in sedimentary basins with strong potential for soil amplification and earthquake-induced damage. As part of this study, we examine city-scale site response in two CEUS cities that reside within basin structures: Memphis, TN, and New York City, NY. We develop shear-wave velocity models from available data and perform theoretical linear one-dimensional site response analyses to estimate site response at multiple ground-motion stations within these cities. We compare the theoretical site response predictions with those from the NGA-East V_S30-based linear amplification model (Stewart et al., 2020) and a linear amplification model proposed in a companion study (Meyer et al., 2025) that is based on geospatial predictor variables (adjusted physiographic province and sediment thickness) rather than V_S30. We also compare the results to observed amplifications from recent earthquakes recorded at ground-motion stations in each city. In Memphis, which is located on deep sediment within the Mississippi Embayment, our proposed model accurately predicts long-period amplification but overestimates short-period amplification compared to the NGA-East model. In New York City, which is located on the edge of the Atlantic Coastal Plain, there are significant variations in sediment thickness. Both linear site amplification models perform better at deep sites than shallow sites, highlighting the difficulty in modeling site response at shallow sediment sites with strong impedance contrasts and the need for higher-resolution sediment thickness data in the entire CEUS. The improved performance of our model in Memphis at longer periods indicates that the explanatory variables of sediment thickness and adjusted physiographic province are useful for estimating site amplifications in regions with deep sediments in the CEUS. This study also highlights the limitations of ergodic ground-motion modeling and the benefits of site-specific or city-scale ground response analysis within vulnerable cities, especially in capturing changing behavior at a smaller spatial scale.

Session: Why Ignore the Structure? Soil-structure Interaction and Site Response at Local and Regional Scales - I

Type: Oral

Date: 4/17/2025

Presentation Time: 11:15 AM (local time)

Presenting Author: James

Student Presenter: No

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