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

Data

Observation

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 Timeline

Activity 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 Timeline

Activity 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 Test

Country/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 Timeline

Activity 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

R1V1 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

R1V1 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

R1V1 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