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NGA Project Review and Status

Detailed overview of developer scope, ground motion models, site classification, and new predictive parameters. Tasks to support NGA developers and associated working groups.

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NGA Project Review and Status

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  1. NGA Project Review and Status Norm Abrahamson NGA Workshop #5 March, 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 • 112 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. Tasks to Support NGA Developers 1. Empirical database development • 1-D rock simulations • Evaluation of source-path predictor variables • Evaluation of site classification and site effects • Site response simulations • Statistical approaches • 3-D basin response simulations • Compilation of seismic network ground motion data for M5 at large distances

  8. Working Groups • Data Processing • Ground Motion Database • Validation of 1-D Rock Motion Simul • Source/Path Effects • Site Classification & Site Effects • Statistical Modeling of Data

  9. NGA Tasks and Associated WGs

  10. Task 1Empirical Database Development • Metadata • Version 1 released in November • Source and path parameters review by Somerville (complete) • Site parameters review by Wells (not complete) • Modifications • Incorporate review comments • Next version due April 23 • Includes rotations to FN and FP

  11. Task 1 (cont)Empirical Database Development • Ground Motion Values • Evaluation of adequacy of processing in progress (comparison of PEER Sa values with CSMIP and USGS Sa values) – WG #1 • Meeting held March 17 • Summary to be given by Abrahamson • Evaluation of treatment of permanent displacements (fling step) – WG#1 • Update to be given by Graves

  12. Task 21-D Rock Motion Simulation • Validations • URS, Silva, Zeng (not complete) • Update to be presented • Simulations • Strike-slip scenarios • URS complete, Zeng nearly complete (missing SJ) • Silva results preliminary (to be updated) • Reverse-slip scenarios • URS complete, Zeng (7 events complete) • Silva results due March 31

  13. Task 3 Evaluation of Source-Path Predictor Variables • Review of Metadata by WG#4 • Source and travel path parameters • Review completed (Somerville) • WG#4 • 1-D rock simulations • Updated scaling results to be shown (Abrahamson) • Directivity model using Isochrons • Spudich working on model refinements • 3-D basin simulations(mtg held Mar 5) • Scale factors to be discussed by Steve Day

  14. Task 4 Evaluation of Site Classification and Site Effects • Review of Metadata (WG#5) • Recording site classification • Structure (building) classification • Review by Wells to be completed April 2 • Review alternative site classification schemes and functional forms for site effects (WG#5) • Evaluate site response simulations and empirical data • Develop method for translations among different site classification schemes (WG#5) • Not started

  15. Task 5 Site Response Simulations • Simulation method • RASCALS with soil randomization • Simulations • Previous PEER-LL and NEHRP studies (Silva) • Augment previous simulations • Identify additional cases needed (April 5) • Results in May • Sensitivity analysis • Comparisons with RASCAL, SHAKE, and Non-linear models • Completed. To be shown by Sun

  16. Task 6 Statistical Approaches • Issues (WG#6) • Review of alternative methods • Weights, two-step, random effects, … • Spatial correlation of ground motion • Correlation of spectra at different frequencies • Standard deviation • Dependence on magnitude, distance, and soil type • Incorporating measurement errors in predictor variables • Missing predictor variables • Censored data (non-triggered stations) • Combining empirical and simulated data in regression analyses (NGA-H) • WG#6 held initial meeting • Scope of work identified • WG#6 recommendations in May

  17. Task 7 3-D Bain Simulations • Program verification completed • Simulations completed • Evaluation of results • Will be presented Thursday

  18. Task 8 Network Data Evaluation • Evaluation of attenuation at large distances using network data • Complete • Presented by Boatwright in WS#4

  19. Revised Schedule • March 24-25 Workshop #5 • April 20 Draft summary of supporting task reports • May 6-7 Developer interaction meeting • June 24-25 NGA workshop #6, • Developers present preliminary model • Developers explain • July 12 Draft report due • Describe approach and preliminary model • For circulation to other developers • July 19-26? Developer interaction meeting • Sep 17 Final models due • Sep 30 Final report due • Oct 14-15 Final workshop • Compare models (other developer’s models and past models) • Examine impacts on hazard

  20. NGA Reports • Data Report • Documentation of data set in flat file • Resource Report • Documentation of results from supporting tasks and working groups • NGA Ground Motion Report • Documentation of the developers models • Summary, Overview, and Impacts

  21. Data Report • Metadata • Documentation of magnitudes, source geometries, site conditions, distances, directivity parameters, HW/FW, etc • Ground motion processing • Causal vs acausal • Filter corners • Fling step removal • QA Efforts • Reviews of metadata and response spectra

  22. Resource Report • Working Group Activities • Scaling factors based on 1-D rock simulations • Basin scaling factors based on 3-D simulations • Directivity functional form based on Isochron • Site response amplification factors • Attenuation rates from network data • Statistical approaches

  23. NGA Ground Motion Model Report • Synthesis of developer’s models • Model report from each developer • Fling step model • (for adding fling back into ground motion)

  24. Summary and Impacts • General report summarizing NGA project • Focus on impacts of new models • How do the new models effects the design ground motions for future projects?

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