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Project Review and Summary of NGA Supporting Research

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

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Project Review and Summary of NGA Supporting Research

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  1. Project Review and Summary of NGA Supporting Research Norm Abrahamson NGA Workshop #6 July, 2004

  2. 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

  3. 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

  4. Developer Scope (cont) • 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

  5. Developer Scope (cont) • 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

  6. Developer Scope (cont) • 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

  7. NGA-E • Primarily Empirically based • Uses analytical models to guide model in regions not well constrained by data

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

  9. 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

  10. 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

  11. 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

  12. 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

  13. PLOTS OF NEHRP SITE CLASS AMPLIFICATION FACTORS FROM SITE RESPONSE SIMULATIONS BY PACIFIC ENGINEERING & ANALYSIS MAY 2004

  14. PRELIMINARY PLOTS OF NEHRP SITE CLASSAMPLIFICATION FACTORS FROMEMPIRICAL STUDIES BY ROGER BORCHERDT, JON STEWART AND MAURY POWER, WORKING GROUP #5 JULY 2004

  15. 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)

  16. Distant Attenuation from Moderate Eqk in Ca Boatwright and Seekins

  17. Southern California

  18. Northern California

  19. Precarious Rocks • Precarious rock studies not funded by NGA, but available results will be considered • Can be used to check the regression models

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