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Turkey Flat, USA Site Effects Test Area: “Blind” Test of Predicted Ground Response of a Shallow Stiff-Soil Site to the September 28, 2004 M6.0 Parkfield Earthquake. Charles R. Real and Anthony F. Shakal California Geological Survey. Hypothesis. Model. Supposition. Specific Case. Validation.
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Turkey Flat, USA Site Effects Test Area: “Blind” Test of Predicted Ground Response of a Shallow Stiff-Soil Site to the September 28, 2004 M6.0 Parkfield Earthquake Charles R. Real and Anthony F. Shakal California Geological Survey
Hypothesis Model Supposition Specific Case Validation Observation Measurement Experimentation Need to Validate Ground Motion Prediction Models Theory Toward Knowledge Data
Background • 1985 IASPEI/IAEE Resolution to: • Promote establishment of test sites around world to validate methods of predicting “effects of surface geology on seismic motion” • Form Joint Working Group to provide guidance for establishing test sites • 1986 CGS/CSMIP established test site at Turkey Flat near Parkfield, CA
“Blind” Test Approach • Conduct high quality field and laboratory tests to characterize the geotechnical properties of the site • Collect high-quality measurements of ground response in sediment basin and bordering rock • Distribute only rock records and request predictions at basin recording sites • Release observed basin recordings of and compare with predictions
Turkey Flat Site Effects Test Area
Field Tests
Seismic Reflection & Refraction Surveys
A’ R2 V2 C C’ V1, D2, D3 B’ R1, D1 A B Turkey Flat Site Effects Test Area Next slide shows profiles
Accelerographs Installed Weak-motion Data Collection Experiment Timeline
Weak Motion Test Country/ParticipantsStandardPreferred Canada (1) 1 1 China (2) 2 Czechoslovakia (2) 2 France (4) 3 1 Germany (1) 1 Italy (3) 1 1 Japan (13) 7 2 Mexico (1) 1 New Zealand (1) 1 USA (13)61 Totals 41 6
R2 V1 V2 R1 D2 D1 D3 Required Strong-Motion Predictions • Fourier Amplitude Spectral Ratios: • 1) Xi/R1 given R1 (where Xi means D1, D2, D3, V1,V2, R2) • 2) V1/D3, D2/D3 given D3 Two-step process: R1 predictions (4 months) Then: D3 predictions (3 months)
R2 V1 V2 R1 D2 D1 D3 Required Strong-Motion Predictions • Acceleration Time Histories: • (1) V1, D2, D3 given R1 • (2) V1, D2 given D3
R2 V1 V2 R1 D2 D1 D3 Required Strong-Motion Predictions • Psuedovelocity Response Spectra (5% damped) & peak values displ, vel, accel: • 1) Xi given R1 (where Xi means D1, D2, D3, V1,V2, R2) • 2) V1, D2 given D3
Terms/Conditions • Predictions are voluntary and at own expense • Required predictions must be complete as requested, and carried out using a “preferred” geotechnical model developed from data provided • All predictions must include estimates of uncertainty • Individuals/groups shall remain anonymous when evaluating/comparing prediction results
Optional Predictions (encouraged) • Full required set as described, but using the “standard” geotechnical model • Time histories for V2, R2 given R1 for “preferred” geotechnical model • Time histories for V2, R2 given R1 for “standard” geotechnical model • Compute vertical components for all predictions
SM Prediction Timeline • Announcement of test 12/2004 • Given-R1 predictions due 9/2005 • Given-D3 prediction begins 10/2005 • Given-D3 predictions due 11/2005 • Workshop Spring 2006
Turkey Flat Working Group Stay Tuned…….. www.quake.ca.gov/Parkfield_2004