Lessons Learned from Fukushima Related to Seismic Hazards at U.S. Nuclear Power Plants and Future Seismic Hazard Studies
October 7, 2014
John G. Anderson Professor of Geophysics
University of Nevada, Reno
10/7/14 1 US NRC: Lessons learned from Fukushima
10/7/14 2 US NRC: Lessons learned from Fukushima
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10/7/14 3 US NRC: Lessons learned from Fukushima
Probabilistic Seismic Hazard
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10/7/14 4 US NRC: Lessons learned from Fukushima
Probabilistic Seismic Hazard
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10/7/14 5 US NRC: Lessons learned from Fukushima
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Science Behind PSHA
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Ground motion prediction equations
Lesson from pre-2011 Hazard Map
• M9 earthquake off the north coast was not included in the model.
– Smaller fault segments expected
– Linkage not considered
• Lesson: need to include fault linkages.
– US National Seismic Model for 2014 does this in California – overcomes this problem.
– Needs to be extended to the rest of the west.
10/7/14 6 US NRC: Lessons learned from Fukushima
Lesson from lost credibility
• Main “evidence” criticizing PSHA – M9 in Tohoku, Haiti, Wenchuan, Christchurch
– Criticism misplaced
• Lesson: – To assure quality PSHA, need an open process
– Ongoing two-way communication with global seismology community
– Goal: pathway for new relevant discoveries be promptly considered, without even waiting for formal updates of hazard maps.
10/7/14 7 US NRC: Lessons learned from Fukushima
Process: U.S. National Seismic Model
• Collaborative, community model
– USGS internal & external research programs
– NRC, EPRI, NSF, PEER, SCEC, …
• Update every 6 years
– Inclusive regional workshops
10/7/14 8 US NRC: Lessons learned from Fukushima
National Seismic Model: Issues
1. Better models for uncertainties
2. Selection of ground motion prediction equations
3. Validation and utilization of synthetic seismograms
4. Basins and long period ground motions
5. Test hazard curves – especially at low probability
6. Time dependence
7. Induced seismicity
10/7/14 9 US NRC: Lessons learned from Fukushima
National Seismic Model: Issue 1
• Better models for uncertainties
• Why? – At low probabilities, uncertainties dominate hazard
estimates, and small changes in uncertainties have a strong effect on results.
• How? – Broadband seismic networks
– Deal with the diversity in earthquake sources
– Ground motion prediction (regionalized)
– Seismic stations at the nuclear facility for local effects.
10/7/14 10 US NRC: Lessons learned from Fukushima
National Seismic Model: Issue 3
• Validation and utilization of synthetic seismograms
• Why? – Where data is sparse, simulations, if credible, can help
reduce uncertainties.
– Many uses in Japan
• How? – Seismic networks provide data to determine Earth
structure and source domains and characteristics.
– Validation exercises
10/7/14 11 US NRC: Lessons learned from Fukushima
National Seismic Model: Issue 6
• Time dependence • Why?
– Some nuclear facilities are near active faults likely to rupture within the facility lifetime.
– Example: Palo Verdi hazard at long periods is dominated by southern San Andreas fault, highly likely to have a an M8 class earthquake in next 30 years
• How? – Paleoseismology research – Appropriately modify the hazard assessment
10/7/14 12 US NRC: Lessons learned from Fukushima
National Seismic Model: Issue 7
• Induced seismicity
• Why? – It is happening
– Could happen in more places
• How? – Depends on
human activity
– Difficult issue
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Thank you
10/7/14 14 US NRC: Lessons learned from Fukushima
Extra Slides
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National Seismic Model: Issue 2
• Selection of ground motion prediction equations
• Why?
– Current process too strongly influenced by judgment
• How?
– Analytical methods to explore GMPE space
– More explicit acceptance criteria
10/7/14 16 US NRC: Lessons learned from Fukushima
National Seismic Model: Issue 4
• Basins and long period ground motions
• Why? – Some geological structures can amplify ground
motions enormously at long periods. (e.g. Mexico City, Hokkaido, Las Vegas, Los Angeles)
– Engineers asking for this
• How? – Broadband instruments for validation data
– Modeling is believed most reliable at long periods
10/7/14 17 US NRC: Lessons learned from Fukushima
National Seismic Model: Issue 5
• Test hazard curves – especially at low probability
• Why? – At low probability, models are
most sensitive to uncertainty
• How – Old fragile geological structures
that have not been damaged by past earthquakes.
– Example: precarious rocks near Yucca Mountain with ages >10,000 Inconsistent with the PSHA.
10/7/14 18 US NRC: Lessons learned from Fukushima
10/7/14 19 US NRC: Lessons learned from Fukushima
(a)
Lessons from Fukushima: Diversity in Earthquakes
--=ii!B B
2011~3-09 2011~3-09(2) 2008~7- 19 2005- 12~2 2003-10-31 (a)
75 L--2....JOOL:------ll 5":-0---....LI 00-:-----5-LO ~ , •• Distance from trench j , •.
Sources: Lay et al. {2012), Ye et al. {2013}, Kanamori {2014)
Acronyms
• PSHA: Probabilistic Seismic Hazard Analysis • GMPE: Ground Motion Prediction Equation • M9: Magnitude = 9 • USGS: US Geological Survey • NRC: Nuclear Regulatory Commission • EPRI: Electric Power Research Institute • NSF: National Science Foundation • PEER: Pacific Earthquake Engineering Research
Center • SCEC: Southern California Earthquake Center
10/7/14 US NRC: Lessons learned from Fukushima 20
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