Affiliation:
1. Geology Branch, Division of Safety of Dams, California Dept. of Water Resources, Sacramento, CA 95818
Abstract
Accurately characterizing near-source ground motion is an important consideration for dam safety in California. Near-source ground motion can contain velocity pulses that are amplified by directivity, which is the constructive interference of S waves radiated by a propagating rupture front. Accordingly, Somerville et. al. (1997) developed an empirical model for predicting fault-normal (maximum) and fault-parallel (minimum) spectral acceleration for periods>0.5 sec. We compiled near-source ground motion records representing significant directivity and rotated them to the component with maximum overall spectral acceleration for common periods of directivity amplification (and importance to dam stability analyses, 0.5≤T≤3.0 sec), which we call SAMAX. As expected, SAMAXcorrelates with the orientation of a strong velocity pulse in the directivity record. Comparing the amplitude and orientation of SAMAXto Somerville's predictions, we find that strong velocity pulses produced by strike-slip faulting are reasonably aligned with the fault normal, and their corresponding SAMAXis satisfactorily predicted by Somerville's model as modified by Abrahamson. However, the orientations of strong velocity pulses in reverse-faulting records can depart significantly from fault normal, and their corresponding SAMAXcan exceed Somerville's predictions appreciably.
Subject
Geophysics,Geotechnical Engineering and Engineering Geology
Cited by
49 articles.
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