Charles R. Real and Anthony F. Shakal California Geological Survey

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

Need to Validate Ground Motion Prediction Models

Theory

DataObservation

Supposition Hypothesis

Measurement

Toward Knowledge

Experimentation

Model

ValidationSpecific Case

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 EffectsTest Area

Experiment TimelineActivity When

1. Geotechnical site characterization 1986

2. Accelerograph Installation 1987

3. Weak-motion data collection 1988-89

4. Weak-motion prediction test 1990

5. Strong-motion data collection ?

6. Strong-motion prediction test ?

FieldTests

Lab Tests

Seismic Reflection

& RefractionSurveys

Turkey Flat Site Effects Test Area

R1, D1

V1, D2, D3

V2R2

B

B’

A

A’

C C’

Next slide shows profiles

Geologic Structure

Experiment TimelineActivity When

1. Geotechnical site characterization 1986

2. Accelerograph Installation 1987

3. Weak-motion data collection 1988-89

4. Weak-motion prediction test 1990

5. Strong-motion data collection ?

6. Strong-motion prediction test ?

Accelerographs Installed

Weak-motion Data Collection

Weak Motion TestCountry/Participants Standard PreferredCanada (1) 1 1China (2) 2Czechoslovakia (2) 2France (4) 3 1Germany (1) 1Italy (3) 1 1Japan (13) 7 2Mexico (1) 1New Zealand (1) 1USA (13) 6 1Totals 41 6

New Experiment TimelineActivity When

1. Geotechnical site characterization 1986

2. Accelerograph Installation 1987

3. Weak-motion data collection 1988-89

4. Weak-motion prediction test 1990

5. M6.0 Parkfield Earthquake 9/28/2004

6. Strong-motion prediction test 2005

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

D3

D2

D1

R1 V1 V2 R2

Two-step process: R1 predictions (4 months)

Then: D3 predictions (3 months)

Required Strong-Motion Predictions

• Acceleration Time Histories:– (1) V1, D2, D3 given R1– (2) V1, D2 given D3

D3

D2

D1

R1 V1 V2 R2

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

D3

D2

D1

R1 V1 V2 R2

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

Workshop Timeline

Workshop When

1. Vancouver, B.C. 1987

2. Tokyo, Japan 1992

3. San Francisco, CA Spring 2006

Turkey Flat Working Group

Stay Tuned……..www.quake.ca.gov/Parkfield_2004