Application of Earthquake Source Modeling to Assess the Relative Differences Between Seismic Ground Motion in the Eastern and Western Regions of the United States and to Characterize the Type and Direction of Incoming Seismic Wave

摘要

This report assesses the relative difference between seismic ground motion in the Eastern (EUS) and Western (WUS) regions of the United States; and provides the necessary input to soil-structure interaction codes concerning type and propagation direction for incoming seismic waves. Implicit is the relevance to the Zion Nuclear Power Plant (ZNPP) site. The relative differences between seismic ground motions in EUS and WUS are assumed to be principally caused by differences in material attenuation. Earthquake rupture and wave propagation through the earth were simulated by performing numerical calculations. Typical results for a Western United States earth structure indicate that essentially no seismic energy emerges at angles shallower than 45 degrees except for low frequency emission from shallow zones of earthquake rupture. The same simulations are repeated for the ZNPP earth structure. The effective incoming waves are seen to be emerging within ten degrees of vertical at Zion for all source/receiver geometries and all frequencies of interest. At high frequency, the reduced material attenuation (corresponding to the higher EUS quality factors) additionally constrains the effective incoming waves to emerge within five degrees of vertical. (ERA citation 07:044868)