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U.S. Geological Survey Open-File Report 94–706

Seismic Velocities and Geologic Logs from Boreholes at Three Downhole Arrays in San Francisco, California

By James F. Gibbs, Thomas E. Fumal, Roger D. Borcherdt, Richard E. Warrick, Hsi-Ping Liu, and Robert E. Westerlund

Thumbnail of and link to report PDF (13.9 MB)Introduction

The Loma Prieta earthquake of October 17, 1989 (1704 PST), has reinforced observations made by Wood and others (1908) after the 1906 San Francisco earthquake, that poor ground conditions (soft soil) increase the likelihood of shaking damage to structures. Since 1908 many studies (for example Borcherdt, 1970, Borcherdt and Gibbs, 1976, Borcherdt and Glassmoyer, 1992) have shown that soft soils amplify seismic waves at frequencies that can be damaging to structures.

Damage in the City of San Francisco from the Loma Prieta earthquake was concentrated in the Marina District, the Embarcadero, and the China Basin areas. Each of these areas, to some degree, is underlain by soft soil deposits. These concentrations of damage raise important questions regarding the amplification effects of such deposits at damaging levels of motion. Unfortunately, no strong-motion recordings were obtained in these areas during the Loma Prieta earthquake and only a limited number (< 10) have been obtained on other soft soil sites in the United States. Consequently, important questions exist regarding the response of such deposits during damaging earthquakes, especially questions regarding the nonlinear soil response. Towards developing a data set to address these important questions, borehole strong-motion arrays have been installed at three locations. These arrays consist of groups of wide-dynamic-range pore-pressure transducers and three-component accelerometers, the outputs of which are recorded digitally. The arrays are designed to provide an integrated set of data on ground shaking, liquifaction-induced ground failure, and structural response. This report describes the detailed geologic, seismic, and material-property determinations derived at each of these sites.

  • This report is also available in print from:

    USGS Information Services, Box 25286,
    Federal Center, Denver, CO 80225
    telephone: 888 ASK-USGS; e-mail: infoservices@usgs.gov

For additional information:
Contact Information, Earthquake Science Center, Menlo Park Science Center
U.S. Geological Survey
345 Middlefield Road, MS 977
Menlo Park, California 94025
http://earthquake.usgs.gov/

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Suggested citation:

Gibbs, J.F., Fumal, T.E., Borcherdt, R.D., Warrick, R.E., Liu, H., and Westerlund, R.E., 1994, Seismic velocities and geologic logs from boreholes at three downhole arrays in San Francisco, California: U.S. Geological Survey Open-File Report 94–706, 40 p. (Available at https://pubs.usgs.gov/of/1994/0706/.)



Contents

Introduction

Field Techniques

Velocity Determinations

Results

Acknowledgments

References

Appendixes A–C


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