1. Treatment of kappa in Recent Western US Seismic Nuclear Plant Probabilistic Seismic Hazard Studies AGU Fall Meeting, 12/17/2015 rev.1 12/20/2015
Gabriel R. Toro, Lettis Consultants International, Inc.
Carola Di Alessandro, GeoPentech, Inc.
Linda Al Atik, Al Atik Consulting

2. Credits: Kappa and kappa-effects Teams; Sponsor Representatives
Hanford & Columbia Generating Station (Eastern Washington State)
J.J. Bommer, L. Al Atik, A. Rodriguez-Marek, G.R. Toro, W.J. Silva, R.R Youngs, B. Bryce, G. Lisle
Palo Verde Nuclear Generating Station (near Phoenix, Arizona)
N. Abrahamson, L. Al Atik, C. Di Alessandro, O. Ktenidou, W.J. Silva, G.R. Toro, C. Wandell

3. Origin and Effects of Kappa (actually, k0 in Anderson-Hough terminology)
from Ktenidou et al. (2015)
Kappa is not a free parameter in most existing GMPEs
(each GMPEs has an implicit kappa)
Origin: Damping and scattering
effects beneath the site
(soil column and shallow crust)
~ exp[-pk0f]

4. Hanford Data Project Requirements:
Recordings at 7 sites (all but one with 20-Hz Nyquist frequency)
8-15 recordings per site
M range
Distance range km
Project Requirements:
Need kappa estimates at 5 sites with no recordings (different thicknesses)
Kappa for a horizon below interbeds (top of Lolo flow)
Soil and basalts
(2,700-7,200 m)
Need k0
here
(below interbeds)
Pre-Miocene Sediments
(700-6,500 m)

5. Approach for kappa estimation
Determine kappa at each recording site
Broadband inversion for kappa, crustal Q model, magnitude, and stress drop (fits entire FAS*)
Anders0n-Hough approach (fit to linear portion of log[FAS]-frequency plot above corner frequency, determine zero-distance intercept)
For application to target sites, investigate relationship between kappa and profiles' thicknesses and velocities
*FAS: Fourier amplitude Spectrum

6. Broadband Inversion kappa
Results
Broadband Inversion kappa
Anderson-Hough kappa

7. Epistemic Uncertainty and Effects
Site A Sa adjustment factors applied to GMPE (also include impedance effects)
Red: no sub-basalt sediments contribute to k

8. Palo Verde - PVNGS (near Phoenix, AZ) Approaches Used
Data Used
2 earthquakes,
M 3.1 and 3.4
6 earthquakes, M
11 earthquakes, M
14 stations
Approach 1
Approach 2
Approach 3

9. Data for Approaches 1 and 2

10. Approaches 1 and 2 Approach 3
Broadband inversion for kappa, magnitude, and stress drop (fix crustal Q model)
Result: kappa=0.033 s (median value across sites
Uncertainty: slnk=0.5
Adopt s with slnk=0.5 as combined model (applies to bottom of soil profile)

11. Adjustment from SWUS Reference Conditions to PVNGS Rock (FAS Space; applied to rock FAS prior to site response analysis)

12. Summary Site-specific kappa is usually difficult to estimate
Few recordings
Bandwidth limitations
Must characterize associated epistemic uncertainty
If site-specific kappa is different from kappa implicit in GMPEs, kappa adjustment may be appropriate
2 examples provided
Large uncertainty/scatter in the adjustments

13. Addendum: Links to References
Hanford-Columbia
PSHA Report: (see chapters on GMC Databases and Ground Motion Characterization, and also Appendix I)
Palo Verde
Target kappa for Arizona: (see Chapter 4)
SWUS Ground Motions Report: (see SWUS Appendices L and M)
Incorporation of target kappa in PSHA: (see Section 2.3)