project review and summary of nga supporting research norm abrahamson nga workshop #6 july, 2004

Project Review and Summary of NGA Supporting Research

Norm Abrahamson

NGA Workshop #6

July, 2004

Developer Scope• Ground Motion Model (median, standard dev)

– Ground Motion Parameters:• Horizontal components (Ave Horiz, FN, and FP)• PGA, PGV, PGD• Pseudo spectral acc at 5% damping: 0-10 sec

– Applicable Magnitude Range:• 5.0 - 8.5 (SS)• 5.0 - 8.0 (RV)

– Applicable Distance Range:• 0 - 200 km

– Fault Types• Strike-slip, Reverse, Normal

– Site Classification Scheme• Developers select their preferred classification scheme• Need not include soft-soil

Developer Scope (cont)

• Ground Motion Data Set– Common data set provided to developers– Each developer selects applicable subset of data

• Justify the exclusion of earthquakes and recording sites• Document any modification of independent parameters from

PEER recommended values• Ground motion values are not modified (e.g. common set

used by all developers), but developers select applicable period range of each recording

– Final selected data to be listed in report


• Evaluate new predictive parameters– Directivity parameters– Hanging wall / foot wall– Static stress-drop– Asperity depth– Depth to bedrock (or Vs)– Basin parameters

• Each developer decides if new predictive parameter is to be included in their model– Justify the selection or rejection of each parameter evaluated


• Spectral Periods– 95 periods provide (from 0.01 to 10 sec– Minimum set of 20 periods required for model:

• 0.02, 0.03, 0.05, 0.075, 0.10, 0.15, 0.20, 0.25, 0.30, 0.40, 0.50, 0.75, 1.0, 1.5, 2.0, 3.0, 4.0, 5.0, 7.5, 10


• Magnitude definition– All developers use moment magnitude

• Distance definition– Developers select appropriate distance metric

• Site classification– Developers select site classification

• Clear definition of site classes

– Provide a translation scheme to NERHP categories

NGA-E

• Primarily Empirically based

• Uses analytical models to guide model in regions not well constrained by data

Supporting Research

• 1-D Rock simulations• 3-D basin simulations• Isochron simulations• Site amplification calculations• Network data evaluation• Precarious Rocks

1-D Rock simulations• Three groups have completed all simulations

– Zeng revised the sub-event stress-drop to be magnitude dependent

– Pacific Engineering completed Rev cases

• Still requires discussion among modelers to explain differences

• Simulations can be used for:– Magnitude scaling above M7 – Period extrapolation to 10 seconds– Directivity scaling– Hanging wall footwall scaling– Shallow vs buried slip– Stress-drop scaling

3-D Basin Simulations

• Simulations previously completed

• Functional form developed for scaling to 10 seconds based on the depth to Vs (1000-2500 m/s) isosurface

Isochron Simulations

• Initial model is complete

• Provides a new parameterization of directivity that covers all source types (with stronger seismological basis)– Comparisons with 1-D rock simulations and

empirical data is being carried out

• Results can be used to constrain directivity

Site Amplification Calculations

• Calculations and formatting of results completed– Functions of PGA on rock– Functions of SA on site class B

• Can be used to constrain site response scaling, with emphasis on non-linear site response scaling

PLOTS OF NEHRP SITE CLASS AMPLIFICATION FACTORS FROM SITE

RESPONSE SIMULATIONS

BY

PACIFIC ENGINEERING & ANALYSIS

MAY 2004

PRELIMINARY PLOTS OF NEHRP SITE CLASSAMPLIFICATION FACTORS FROM

EMPIRICAL STUDIES

BY

ROGER BORCHERDT, JON STEWART

AND MAURY POWER, WORKING GROUP #5

JULY 2004

0 0.1 0.2 0.3 0.4 0.5 0.6

PGA (g)

0

0.5

1

1.5

2

2.5

3

3.5

4

Fa (0.3 sec)

SITE CLASS C, FaBorcherdt (2002)

Stewart et al. (2003)

Choi & S tewart (2004)

Rodriguez - M arek et al. (1999)

Field (2000)

Stei dl (2000)

Harmsen (1997)

Borcherdt (1994)

Crouse & M cGuire (1996)

Joyner & Boore (2000)

Dobry et al. (1999)

Silva et al. (2000)

NEHRP (1997)

0 0.1 0.2 0.3 0.4 0.5 0.6

PGA (g)

0

0.5

1

1.5

2

2.5

3

3.5

4

Fa (0.3 sec)

SITE CLASS D, FaBorcherdt (2002)




Field (2000)

Stei dl (2000)

Harmsen (1997)

Borcherdt (1994)



Dobry et al. (1999)

Silva et al. (2000)

NEHRP (1997)

0 0.1 0.2 0.3 0.4 0.5 0.6

PGA (g)

0

0.5

1

1.5

2

2.5

3

3.5

4

Fa (0.3 sec)

SITE CLASS E, FaStewart et al. (2003)


Borcherdt (1994)

Silva et al. (2000)

NEHRP (1997)

0 0.1 0.2 0.3 0.4 0.5 0.6

PGA (g)

0

0.5

1

1.5

2

2.5

3

3.5

4

Fv (1.0 sec)

SITE CLASS C, FvBorcherdt (2002)




Field (2000)

Stei dl (2000)

Harmsen (1997)

Borcherdt (1994)



Dobry et al. (1999)

Silva et al. (2000)

NEHRP (1997)

0 0.1 0.2 0.3 0.4 0.5 0.6

PGA (g)

0

0.5

1

1.5

2

2.5

3

3.5

4

Fv (1.0 sec)

SITE CLASS D, FvBorcherdt (2002)




Field (2000)

Stei dl (2000)

Harmsen (1997)

Borcherdt (1994)



Dobry et al. (1999)

Silva et al. (2000)

NEHRP (1997)

0 0.1 0.2 0.3 0.4 0.5 0.6

PGA (g)

0

0.5

1

1.5

2

2.5

3

3.5

4

Fv (1.0 sec)

SITE CLASS E, FvStewart et al. (2003)


Borcherdt (1994)

Silva et al. (2000)

NEHRP (1997)

Moderate Eqk Attenuation

• Results completed for Southern and Northern California

• Model parameterized in terms of anelastic attenuation for a given geometrical spreading

• Results can be used to constrain the moderate magnitude attenuation at large distances (> 70 km)

Distant Attenuation from Moderate Eqk in Ca

Boatwright and Seekins

Southern California

Northern California

Precarious Rocks

• Precarious rock studies not funded by NGA, but available results will be considered

• Can be used to check the regression models

project review and summary of nga supporting research norm abrahamson nga workshop #6 july, 2004

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