Loma Prieta Earthquake: Response of San Francisco Bay Deep Fill Deposits to Cyclic Loading

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This research program is part of the initiative to collect perishable data resulting from the 17 October 1989 Northern California (Loma Prieta) earthquake. It was observed that the specific geotechnical conditions at a site and the thickness of the soft soil deposits had a significant influence on the distribution of damage and apparent intensity of shaking during the earthquake. Immediately following the earthquake, the U.S. Geological Survey (USGS) undertook the installation, in the most severely damaged areas of San Francisco and Oakland, of strong motion instruments on the ground surface and in deep boreholes on top of bedrock. Undisturbed soil samples were recovered from all the significant geologic units within the soil profile during the drilling operations. These samples contain information that can be used to perform full dynamic site response analyses for both post-mortem investigations of the site response, and for prediction of the future response to strong ground shaking. The objective of this study is to obtain this information through appropriate classification tests and dynamic response tests performed on these soil samples, and to combine this information with in-situ shear wave velocity measurements obtained by the USGS: this will result in a full description of the dynamic response characteristics of the soil deposit. The results are to be presented as a report containing the complete stress-strain data as well as the derived modulus and damping ratio as a function of strain.