The Earthquake Engineering Online Archive

Synthesized strong ground motions for the seismic condition assessment of the eastern portion of the San Francisco Bay Bridge

Bolt, Bruce A.; Gregor, Nicholas J.

UCB/EERC-93/12, Earthquake Engineering Research Center, University of California, Berkeley, 1993-12, 217 pages (340/B64/1994)

The assessment of the seismic condition of the eastern portion of the San Francisco Bay Bridge began with the definition of realistic seismic strong ground motions which might be expected within the lifespan of the structure. The task of this research program was the construction of synthetic ground motion records which would define adequately the largest seismic ground motions that the bridge could experience in its lifetime. For the Bay Bridge, there are two major seismogenic sources that dominate: the Hayward fault and the San Andreas fault. Source and scaling parameters were selected for each seismogenic source and the research program constructed synthetic time histories for both a Hayward safety evaluation earthquake (SEE) and a San Andreas SEE. To ensure that the synthetic time histories contained sufficient energy in all of the frequencies of engineering and seismological relevance, a separate target acceleration response spectrum was selected for the horizontal and the vertical components of motion. As a final step, the coherency of the synthetic time histories was checked against a coherency model developed for the Bay Bridge based on the three component strong ground motion records from the two neighboring sites in Gilroy from the 1989 Loma Prieta earthquake.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-93-12.pdf (12 MB)