Comparison of Synthetic Pseudoabsolute Response Spectral Acceleration (PSA) for Four Crustal Regions within Central and Eastern North America (CENA)

Abstract

Abstract This study contributes to the development of a new ground‐motion model for Central and Eastern North America (CENA). We evaluate the impact of the seismic‐velocity structure for different crustal regions on ground‐motion measures. We present an overview of the regionalization of the crustal structure of CENA, the physical parameters used for the simulation codes, and the statistical method applied for the comparison of pseudoabsolute response spectral accelerations (PSAs) of four crustal regions defined within CENA. The four crustal regions are (1) the Atlantic Coastal Plain (ACP), (2) the Appalachians (APP), (3) Central North America (CNA), and (4) the Mississippi Embayment/Gulf Coast (MEM). For each region and its statistically representative velocity structure, PSA matrices were computed, covering response oscillator frequencies from 0.5 to 20 Hz and hypocentral distances up to 500 km. PSA matrices for earthquakes at four different focal depths (5, 10, 20, and 30 km) were calculated. The developed method of the normed mean differences gives a meaningful measure for inter‐regional differences of ground motions in comparison with intra‐regional variability. In this study, we compare the ln(PSA) of the APP, ACP, and MEM region with the reference region CNA, respectively. The percentage of ln(PSA) mean difference values that are smaller than the ln(PSA) standard deviation of the reference region CNA lies between 73% and 91% for the APP region, dependent on the focal depth. For the ACP region, it is about 70% for all focal depths, except for the 20 km source depth, which was excluded because a layer boundary at 20.5 km causes unrealistically strong reflections. The percentage for the MEM region is less than 50% for each of the focal depths. This analysis demonstrates that there are two distinct ground‐motion groups for CENA: Group 1: CNA, APP, and ACP Group 2: MEM. Electronic Supplement: Figures of crustal velocity structures, table of Q studies, and Q studies illustrated for one region.