Engineering Characterization of Earthquake Ground Motions.

Abstract

In recent years, geologic and paleoseismic evidence has raised the awareness about the seismic hazard of the stable continental region of central-eastern U.S. (CEUS). The relevance of this topic increased due to the Nation’s renewed interest in the construction of new nuclear power plants in the CEUS and due to the occurrence of the M5.2 earthquake in southern Illinois in 2008. However, few ground motion predictive relations suitable for use in engineering design are available for stable continental regions, due to the paucity of strong ground motion recordings in the region. In this regard, McGuire et al. (2001) generated a database of scaled ground motions for stable continental regions for use in detailed engineering analyses. McGuire et al. developed the motions using a state-of-the-art scaling technique.

Using McGuire et al.'s strong ground motion database, this study has developed empirical ground motion predictive relations for stable continental regions. To develop these relations, an advanced regression technique (i.e., non-linear mixed effects modeling) was used to correlate various ground motion characteristics used in engineering design to earthquake magnitude, site-to-source distance, and local site conditions (i.e., rock vs. soil). Similar predictive relations were developed in this study for active shallow crustal regions (e.g., western U.S.: WUS) using recorded motions, which allowed the ground motion characteristics of the two different tectonic regions to be compared.

The comparison showed that the CEUS motions have distinct characteristics from WUS motions. Firstly, the characteristic period of CEUS motions are systematically shorter than those of WUS motions. However, the strong ground motion duration in CEUS tends to be longer than in WUS. Also, CEUS motions had consistently larger intensities than WUS motions. Finally, the number of equivalent stress cycles (Green, 2001) for CEUS motions is larger and varies more as a function of depth than WUS motions; this trend is consistent with the identified trends in the number of equivalent strain cycles (Green and Lee, 2006).