1. Further Development of Site Response in NGA Models PEER Lifelines Program NGA-West2 Project Topic #8 Working Group Meeting Kickoff MeetingApril 20, 2010

2. Agenda 10 am: Welcome/logistics (Stewart/Bozorgnia) 10:10 am: NGA-West2 overview and project objectives (Bozorgnia) 10:30 am: Background on NEHRP site factors (Borcherdt) 11:00 am: Results from previous NGA Site Factor Working Group (Power) 11:30 am: Comparison of NGA-West site terms to NEHRP (Stewart/Seyhan) Noon: Lunch 1 pm: Open discussion of project objectives, scope, deliverables, & schedule

3. Project Management Yousef Bozorgnia, PEER, NGA-West2 Project Manager Jonathan P. Stewart, UC Los Angeles (Working Group Chair) Emel Seyhan, UC Los Angeles (GSR)

4. Working Group Committee (WGC) Don Anderson, CH2MHill, Bellevue, WA (Geotechnical engineer, TS3 Member) Roger Borcherdt, USGS, Menlo Park, CA (Engineering seismology, developer of NEHRP site factors) C. B. Crouse, URS Corporation, Seattle, WA (Geotechnical engineer, TS3 Chair and PUC Member) R.W. Graves, URS, Pasadena, CA (Seismologist, ground motion simulation and basin effects) I.M. Idriss, UC Davis, Santa Fe, NM (Geotechnical engineer, GMPE developer) Maury Power, AMEC Geomatrix, Oakland, CA (Geotechnical engineer, for TS3 Chair) Walter Silva, PEA, El Cerrito, CA (Seismologist, NGA database manager, GMPE developer) Thomas Shantz, Caltrans, Sacrament, CA (Geotechnical engineer)

5. Do we need others? Working Group Committee (WGC)

6. Database provided by NGA-West2 (PEA) Technical work by UCLA researchers Oversight of work direction/results by WGC Oversight of WGC by …? Deliverables: –Check of NGA-W models (trends with V s30, nonlinearity, sigma) –Evaluate basin depth effects –Develop technical basis for, and consensus behind, revisions to NEHRP site factors Logistics

7. Agenda 10 am: Welcome/logistics (Stewart/Bozorgnia) 10:10 am: NGA-West2 overview and project objectives (Bozorgnia) 10:30 am: Background on NEHRP site factors (Borcherdt) 11:00 am: Results from previous NGA Site Factor Working Group (Power) 11:30 am: Comparison of NGA-West site terms to NEHRP (Stewart/Seyhan) Noon: Lunch 1 pm: Open discussion of project objectives, scope, deliverables, & schedule

8. NGA-West2 Overview and Project Objectives Yousef Bozorgnia

9. Background on NEHRP Site Factors Roger Borcherdt

10. Results from Previous NGA Site Factor Working Group Maury Power

11. Agenda 10 am: Welcome/logistics (Stewart/Bozorgnia) 10:10 am: NGA-West2 overview and project objectives (Bozorgnia) 10:30 am: Background on NEHRP site factors (Borcherdt) 11:00 am: Results from previous NGA Site Factor Working Group (Power) 11:30 am: Comparison of NGA-West site terms to NEHRP (Stewart/Seyhan) Noon: Lunch 1 pm: Open discussion of project objectives, scope, deliverables, & schedule

12. Outline Evaluation of Site Factors –Available approaches –Approaches adopted in NEHRP and NGA GMPEs –Input parameters Comparison of NGA & NEHRP site terms

13. Evaluation of Site Factors Simulation driven: –Computational model, 1D or 3D V s Input Rock Att. G/G Max D  Output

14. Evaluation of Site Factors Simulation driven: –Computational model, 1D or 3D Day et al. 2008

15. Evaluation of Site Factors Simulation driven: –Computational model, 1D or 3D –Randomized soil properties and input motions (1D only) Walling et al. 2008

16. Evaluation of Site Factors Simulation driven: –Computational model, 1D or 3D –Randomized soil properties and input motions (1D only) Walling et al. 2008

17. Evaluation of Site Factors Simulation driven: –Computational model, 1D or 3D –Randomized soil properties and input motions (1D only) –Site factors from simulation results Walling et al. 2008

18. Evaluation of Site Factors Simulation driven: –Computational model, 1D or 3D –Randomized soil properties and input motions (1D only) –Site factors from simulation results Day et al. 2008

19. Evaluation of Site Factors Simulation driven: –Computational model, 1D or 3D –Randomized soil properties and input motions (1D only) –Site factors from simulation results Day et al. 2008

20. Evaluation of Site Factors Simulation driven: –Not used as “stand alone” factors for active regions –Used to constrain certain aspects of “hybrid” models

21. Evaluation of Site Factors Simulation driven Empirical (reference site approach) –Single event –IM soil /IM ref : evaluate dependence on site condition and PGA ref Borcherdt 2002

22. Evaluation of Site Factors Simulation driven Empirical (reference site approach) Empirical (non-reference site approach) –Multiple events –Analysis of residuals –Evaluate dependence on site condition, PGA rock, etc. Choi & Stewart 2005

23. Evaluation of Site Factors Simulation Empirical: Ref. Site Empirical: Non-Ref. Site

24. Evaluation of Site Factors Simulation Empirical: Ref. Site Empirical: Non-Ref. Site NEHRP Factors Nonlinearity Weak Motion Amplification

25. Evaluation of Site Factors Simulation Empirical: Ref. Site Empirical: Non-Ref. Site NGA: AS, CB Nonlinearity Amplification level; V s30 - dependence

26. Evaluation of Site Factors Simulation Empirical: Ref. Site Empirical: Non-Ref. Site NGA: BA, CY Nonlinearity; Amplification level; V s30 - dependence

27. Evaluation of Site Factors Input parameters: –NEHRP: V s30, S s, S 1 –AS: V S30, Median PGA 1100 –BA: V S30, Median PGA 760 –CB: V S30, Median PGA 1100 –CY: V S30, Median +  i (S a ) 1130

28. NGA-NEHRP Comparisons In natural log units, site term = F x (V s30, A x ) –F x =amplification relative to V s30 =x site condition –A x =ground motion amplitude for reference site condition of V s30 =x Use V s30 =150, 270, 560, 760, and 1100 m/s Evaluate F at T=0.3 and 1.0 sec.

29. NGA-NEHRP Comparisons A x : –A=median PGA for AS, BA, CB –A=S a at period of interest for CY (median +  i ); Take S a (0.3)=2.5×PGA and S a (1.0)=1.0×PGA Adopt reference condition of 760 m/s –F 760 (V s30, A x )=F x (V s30, A x )-F x (760, A x )

30. NEHRP E DCBB

31. Suggestions on NEHRP-NGA comparisons Average Sa across all NGA periods in the ranges for Fa and Fv. Use average of logs + limits. Exact middle of the range too (e.g. 0.3 sec for Fa, 1.2 sec for Fv) Average across velocities in site class: use wt average based on histograms of Vs30. Ask Brian how he plotted F vs PGA Check coding using full models. Check NGA errata for AS

32. Residuals Analysis WS: run NGA for 760 with NEHRP factors and look at residuals. –All sites and estimates Vs only Use GMRotI50 New data: –Use June 2010 version of NGA flat file –Alan Yong, USGS: he has funding to perform site investigations. His site list has been approved, previous efforts to provide input on sites to investigate have been resisted

33. Residuals Analysis New data: –Residuals analysis, including Baja earthquake data, focusing on low Vs30 range.

34. Other recommendations USGS maps for all Vs30s, with interpolation (next generation of mapping) When we have the new factors, compare hybrid predictions with them & old factors with full psha for various sites in Nor Cal and So Cal. Check sites without Vs using Virtual Geotechnical Data Center (TS will send url and password). Google earth file with CA stations, see where E stations are (look at other categories too).

35. NGA-NEHRP Comparisons Differences: NEHRP F v high –Esp for C to E NEHRP nonlinearity stronger for C to D NEHRP F a and F v high for rock (Class B)

36. Working Group Objectives & Scope

37. Objectives Input to NGA-West2 developers Develop technical basis for, and consensus behind, revisions to NEHRP site factors –Problems with medians –Different sigmas

39. Task Order Scope Database