1. Sigma - Background Norm Abrahamson Sep 30, 2009

2. Sigma for CEUS EPRI (2006) –Truncation of log-normal distribution –Evaluation of Application of NGA sigma to CEUS Rhoades (2008) –Deviation from log-normal for the upper tail

3. PGA Standard Deviation WUS vs CEUS

4. 2005 versions of NGA Models for WUS Show Constant Sigma

5. EPRI (2004) models and AS NGA (2005 version)

7. Depth Effects on Rjb-Based Models

8. Rjb-Based residuals

9. Flinn-Engdahl regionalization Red = active Blue = Oceanc Yellow = Stable Green = Classified Stable but considered active or oceanic

12. Half Durations RegionNStd dev of half duration (ln units) Active4990.30 ± 0.01 Stable subset 1810.29 ± 0.02 Stable subset 2590.27 ± 0.02 Stable subset 3390.25 ± 0.03

13. Additional Source Parameters in NGA models NGA has additional parameters –Style-of-faulting –Hanging wall / foot wall Small impact on total std dev –Increase by less than 0.01 if these are ignored

14. Path Term Variability Effects of Crustal Structure differences –Used Simulations for range of crustal structures –Compared std dev of resulting ground motions

15. Comparison of velocity structures

17. Stations used for Simulations

18. SCR Simulations

19. WUS Simulations

20. Std Dev for Path Effects ActiveStable PGA0.200.16 25 Hz0.210.17 10 Hz0.230.17 5 Hz0.230.21 2 Hz0.210.20 1 Hz0.330.30 0.5 Hz0.330.28

21. Site Term Variability F=25 Hz Std Dev for Hard -rock (0.55) is larger than for soft-rock (0.51) 5-10 hz for soft-rock is 0.55 - 0.65

22. Std Dev from Stress-Param Variability High Freq Inter-Event Std Dev = 0.43 Compared to NGA values of 0.4

23. EUS Sigma Models Intra-Event Std Dev (R>20 km) –NGA models considered to be applicable with following modifications Increase the std dev to account for source parameters included in NGA that are not available for CEUS (0.01 units) Increase std dev at high frequencies to account for freq content difference –Alternative models More homogeneous crust in CUES (reduce 0.03 units) No reduction

24. EUS Sigma Models Inter-Event Std Dev models –NGA models are applicable without change based on teleseismic comparison –Use std dev from point-source stress parameters distribution

25. EUS Sigma Models Intra-Event Standard Deviation at Short distances –No increase –Some Increase Based on trends from European data –Increase Increase

26. EPRI (2006) model R>20 km

27. Short Distance Sigma Adjustment Model

28. Total Std Dev Models

29. EPRI (2004) models and AS NGA (2005 version)

30. Mag Dependent Sigma? After EPRI (2006) study, some NGA models revised to use mag-dependent sigma –AS08, CY08, I08 –Based on inclusion of aftershocks

31. Standard Deviation (RJB=30 km, VS30=760)

32. Rhoades et al (2008) Method

33. Problems Using Total Residuals

34. AS08 Model Using Intra-Event Residuals

35. AS08 Intra-Event std dev

36. Standard Deviation (M=7, VS30=270)

37. Non-linear site effects T=0.15 sec

38. Evaluation of Inter-Event