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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.