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R. D. Borcherdt, G. Glassmoyer, C. Dietel, and R.E. Westerlund

The Integrated Surface and Borehole Strong-Motion, Soil-Response Arrays in San Francisco, California. R. D. Borcherdt, G. Glassmoyer, C. Dietel, and R.E. Westerlund. COSMOS Geotechnical Strong-Motion Array Workshop 1 University of Southern California October 14-15, 2004 Los Angeles, CA.

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R. D. Borcherdt, G. Glassmoyer, C. Dietel, and R.E. Westerlund

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  1. The Integrated Surface and Borehole Strong-Motion, Soil-Response Arrays in San Francisco, California R. D. Borcherdt, G. Glassmoyer, C. Dietel, and R.E. Westerlund COSMOS Geotechnical Strong-Motion Array Workshop 1 University of Southern California October 14-15, 2004 Los Angeles, CA

  2. Integrated Surface and Borehole Strong-Motion Arrays in San Francisco, CA

  3. Vs30 and Geologic UnitsIntegrated Surface and Borehole Strong-Motion Arrays, San Francisco, CA

  4. Bessie Charmichael School Chevron Building Embarcadero Plaza Embarcadero 4 Bldg. Trans America Bldg. Levi Plaza Marina (WS School) Location of Borehole and Structural-Response Arrays San Francisco, CA

  5. Bessie Charmichael School Location of Borehole Array at Bessie Charmichael School San Francisco, CA

  6. Seismic and Geologic Logs for Array at Bessie Charmichael School

  7. Trans America (USGS) Embarcadero Four (CDMG) Embarcadero Plaza Array (USGS) Location of Borehole Array and Nearby Well-Instrumented Buildings near Embarcadero Plaza San Francisco, CA

  8. Seismic and Geologic Logs for Array at Embarcadero Plaza

  9. Telegraph Hill Levi Plaza Location of Borehole Array and Surface Recorder on Rock near Levi Plaza San Francisco, CA

  10. Seismic and Geologic Logs Levi PlazaBorehole Array

  11. Telegraph Hill Fisherman’s Warf Marina Locations Near Marina Array in San Francisco, CA

  12. Seismic and Geologic Logs for Array at Winfield Scott School

  13. GOES Satellite GEOS GOESReceiver Menlo Park, CA Instrumentation Configuration

  14. Epicenter and Shaking IntensityGilroy, CA Earthquake, M=4.9

  15. Recorded NS Acceleration Recorded EW Acceleration Soft Soil Soft Soil Stiff Soil - Soft Rock Stiff Soil - Soft Rock Firm to Hard Rock Firm to Hard Rock Surface Recordings of NS & EW AccelerationGilroy Earthquake, M=4.9

  16. Epicenter and Shaking Intensity Yountville, CA Earthquake, M=5.1

  17. Embarcadero PlazaYountville Earthquake, M=5.1, 100 seconds • Surface - Z • N-S • E-W • 10 Meters - Z • N-S • E-W • 49.4 Meters - Z • N-S • E-W • 79.2 Meters - Z • N-S • E-W

  18. Surface - Z • N-S • E-W • 10 Meters - Z • N-S • E-W • 49.4 Meters - Z • N-S • E-W • 79.2 Meters - Z • N-S • E-W Embarcadero PlazaYountville Earthquake, M=5.1, 50 seconds

  19. Embarcadero Plaza Spectral Ratio (Surface NS / 79 Meters NS)Yountville Earthquake, M=5.1

  20. Embarcadero Plaza Spectral Ratio (Surface EW / 79 Meters EW)Yountville Earthquake, M=5.1

  21. Embarcadero Plaza Spectral Ratio (10Meters NS / 79 Meters NS)Yountville Earthquake, M=5.1

  22. Embarcadero Plaza Spectral Ratio (10Meters EW / 79 Meters EW)Yountville Earthquake, M=5.1

  23. Embarcadero Plaza Spectral Ratio (50Meters NS / 79 Meters NS)Yountville Earthquake, M=5.1

  24. Embarcadero Plaza Spectral Ratio (50Meters EW / 79 Meters EW)Yountville Earthquake, M=5.1

  25. Surface - Z • N-S • E-W • 30.3 Meters - Z • N-S • E-W • 88.4 Meters - Z • N-S • E-W San Francisco Marina AccelerationYountville Earthquake, M=5.1, 50 seconds

  26. Surface - Z • N-S • E-W • 30.3 Meters - Z • N-S • E-W • 88.4 Meters - Z • N-S • E-W San Francisco Marina Recorded VelocityYountville Earthquake, M=5.1, 50 seconds

  27. Ratio of Recorded Acceleration Ratio of Recorded Velocity San Francisco Marina Acceleration and Velocity Spectral RatiosSurface NS / 88 Meters NS; Yountville Earthquake, M=5.1

  28. San Francisco Marina Spectral Ratio (Surface EW / 88 Meters EW)Yountville Earthquake, M=5.1

  29. Surface – Z • N-S • E-W • 36.9 Meters - Z • N-S • E-W • 89.9 Meters - Z • N-S • E-W Bessie Carmichael School AccelerationYountville Earthquake, M=5.1, 50 seconds

  30. Bessie Carmichael Spectral Ratio (Surface NS / 90 Meters NS)Yountville Earthquake, M=5.1

  31. Bessie Carmichael Spectral Ratio (Surface EW / 90 Meters EW)Yountville Earthquake, M=5.1

  32. Bessie Carmichael Spectral Ratio (37 Meters NS / 90 Meters NS)Yountville Earthquake, M=5.1

  33. Bessie Carmichael Spectral Ratio (37 Meters EW / 90 Meters EW)Yountville Earthquake, M=5.1

  34. Recorded Velocity PRS 21-APR-04 Soft Soil Soft Soil 2470836N2.CPS H181 2470836N2.E0A H181 100 2470836O2.C0A H181 80 2470836N2.BMA H181 60 2470836N2.GAL H181 CM/S**2 40 Stiff Soil - Soft Rock 2470836O2.M0A H181 Stiff Soil - Soft Rock 20 2470836N2.MAR H181 Firm to Hard Rock Firm to Hard Rock 0 0 10 20 30 S Simultaneous Surface Recordings of Radial Acceleration and VelocityYountville Earthquake, M=5.1 Recorded Acceleration 2470836O2.PBS H181 2470836N2.P50 H181 2470836N2.RHL H181 2470836N2.FM3 H181

  35. Amplitude Spectral Ratio to Surface Rock (FM3- Radial -Yountville)

  36. Site-Dependent Response Spectra(linear-linear scale)(NEHRP, UBC, IBC, ASCE 7 Provisions)

  37. Spectral Amplification Dependence on Shear Wave Velocity (Vs)Loma Prieta Earthquake; Ia< 0.1g (Borcherdt, 1994)

  38. Short and Mid-Period Site Coefficients versus Vs30Fa and Fv for Ia< 0.1g (Borcherdt, 1994)

  39. Empirical Measurements of Fa at SF Array SitesFa versus Vs30 Inferred from Loma Prieta Sites

  40. Empirical Measurements of Fv at SF Array SitesFv versus Vs30 Inferred from Loma Prieta Sites

  41. Integrated Surface and Borehole SF Arrays provide important opportunity to measure in-situ high-strain constitutive properties of soft soils in SF region during a large earthquake. Low-strain measurements to date on the array show large period-dependent (resonance) amplification characteristics at sites underlain by thick layers of soft soil. Low-strain site response characteristics observed on SF arrays are consistent with those observed from previous low-strain comparative ground response measurements (Borcherdt et al., 1970, 1975, 1994). Site coefficients, Fa and Fv, measured at some Thick, Soft-soil SF array sites are significantly greater, statistically, than those adopted in current code provisions. Thick, Soft-soil, site-class E and D sites suggested for special-study considerations are those underlain by soils with Vs30 < 225 m/s, and interval Vs < 275 m/s to depths > 30 m. Conclusions

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