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OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS (NMSS) DIVISION OF HIGH-LEVEL WASTE REPOSITORY SAFETY and CENTER FOR NUCLEAR WASTE REGULATORY ANALYSES (CNWRA) and DEPARTMENT OF EARTH, MATERIAL, AND PLANETARY SCIENCES (DEMPS)

JOINT TRIP REPORT

SUBJECT: Participation in the Geological Society of America Penrose Conference: Kinematics and Geodynamics of Intraplate Dextral Shear in Eastern and Western (Al 06002.01.292.542)

DATE/PLACE: April 21-26, 2005, Mammoth Mountain Inn, Mammoth Lakes, California

AUTHORS: John A. Stamatakos, CNWRA David A. Ferrill, DEMPS Philip S. Justus, NMSS

DISTRIBUTION:

CNWRA NRC SwRI

W. Patrick W. Reamer Record Copy B, IQS B. Sagar B. Meehan CNWRA Directors D. DeMarco CNWRA Asst. Directors E. Whitt CNWRA Managers T. McCartin D. Ferrill D. Higgs L. Gutierrez E. Collins L. Kokajko F. Brown K. Stablein M. Bailey J. Guttmann A. Campbell J. Rubenstone K. Compton A. Ibrahim M. Nataraja B. Leslie J. Trapp OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS (NMSS) DIVISION OF HIGH-LEVEL WASTE REPOSITORY SAFETY and CENTER FOR NUCLEAR WASTE REGULATORY ANALYSES (CNWRA) and DEPARTMENT OF EARTH, MATERIAL, AND PLANETARY SCIENCES (DEMPS)

JOINT TRIP REPORT

SUBJECT: Participation in the Geological Society of America Penrose Conference: Kinematics and Geodynamics of Intraplate Dextral Shear in Eastern California and Western Nevada (Al 06002.01.292.542)

DATEIPLACE: April 21-26, 2005, Mammoth Mountain Inn, Mammoth Lakes, California

AUTHORS: John A. Stamatakos, CNWRA David A. Ferrill, DEMPS Philip S. Justus, NMSS

SENSITIVITY: Non-sensitive

BACKGROUNDIPURPOSE: The Yucca Mountain site is in the zone of influence of the Eastern California Shear Zone and the western Nevada tectonic zone called the Walker Lane (Figure 1). Interpretations of the tectonics of the plate boundary and the Walker Lane are critical components of the DOE seismic and volcanic hazard assessments. Staff from NMSS and its contractors at CNWRA are reviewing the tectonic information at the proposed high-level waste repository at Yucca Mountain, especially with respect to how the tectonic information impacts current Department of Energy (DOE) information regarding the seismic and volcanic hazards at the Yucca Mountain site. This Penrose Conference provided an extraordinary opportunity to interact with the scientific community and to learn of the latest tectonic concepts applicable to hazard assessments of Yucca Mountain. In particular, the meeting fostered extensive information exchange on the range of geological and geophysical data that are used to discern how the Walker Lane accommodates tectonic strains from the margin coupled with mantle-crustal thermal-mechanical stresses, and how these data sets are being integrated into spatially and kinematically coherent and comprehensive models of crustal deformation through time. The meeting also provided the opportunity for staff to obtain peer comments from the larger scientific community on CNWRA studies in the region, and of the tectonic models currently considered important in our prelicensing evaluations of the DOE hazard studies for Yucca Mountain.

1 Figure 1. Digital Elevation Model of Western United States Topography with Annotations That Show the Locations of Site and Geologic Features Described In the Trip Report.

2 The meeting was attended by nearly five dozen scientists covering a range of geologic and geophysical disciplines, including tectonics, seismology, paleoseismology, geodesy, volcanology, tectonic geomorphology, paleoclimatology, tectonic sedimentology, and sedimentary basin analysis. There are no formal conference proceedings. The conference format is structured around keynote lectures (two per session topic) followed by moderator-led discussions. In addition to the keynote lectures and discussions, there were poster sessions each evening that also focused on the session topics. Finally, the conference included a one- day field trip that examined geologic evidence of -slip and deformation along the White Mountain, Queen Valley, and Coaldale faults. This trip report summary is based on our impressions from the informal presentations, unpublished abstracts and posters, and discussions held throughout the conference. The Technical Sessions and keynote lectures were:

1. Regional Plate Tectonic and Geologic Setting * Tanya Atwater (University of California at Santa Barbara): Plate tectonic reconstruction and late Cenozoic deformation budget of western North America * Brian Wernicke (California Institute of Technology): Geologic reconstructions

2. Eastern California Shear Zone-Geodesy and Geology

* Rick Bennett (University of Arizona): Geodetic deformation rates in the eastern California shear zone * Doug Walker (University of Kansas): Slip Rates and slip gradients in the eastern California shear zone-the geology

3. Walker Lane Belt-Geodesy and Geology

* John Oldow (University of Idaho): Crustal anisotropy, strain localization, and the development of transtensional strain partitioning during the late Cenozoic evolution of the central Walker Lane, western Great Basin

* Jim Faulds (Nevada Bureau of Mines & Geology, University of Nevada at Reno): Kinematics of northern Walker Lane: An incipient along the Pacific-North American plate boundary

4. Links Among Climate, Tectonics, and Geomorphology * Eric Kirby (Penn State University): Tectonic insight from topographic observations: Does it really work? * Kelin Wipple (Massachusetts Institute of Technology): Tectonics and Topography: What's in it for me?

3 5. Interplay Between Magmatism and Tectonics * Allen Glazner (University of North Carolina): Space-time patterns of late Cenozoic magmatism in eastern California and western Nevada

* Chris Henry (Nevada Bureau of Mines & Geology, University of Nevada at Reno): Coupled magmatic-tectonic evolution of the Walker Lane, western Nevada and eastern California

6. Recent Geodynamic Evolution of the Eastern California Shear Zone and Walker Lane Belt * Kevin Furlong (Penn State University): Lithospheric geodynamics of the eastern California shear zone

* Gene Humphreys (University of Oregon): Walker Lane dynamics

SUMMARY OF PERTINENT POINTS: The following paragraphs summarize some of the concepts, data, interpretations, and conclusions from the keynote sessions that are relevant to potential seismic and volcanic hazards at Yucca Mountain. We have focused on two main themes of the presentations, the application of geodetic measurements to hazard estimates and the nature and style of faulting in the southern Great Basin.

Role of Geodetic Measurement In Hazard Assessments There is a general consensus among the participants that, throughout the Great Basin and Walker Lane, crustal strain rates derived from Global Positioning Satellite (GPS) geodetic data are higher than strain rates derived from geologic and paleoseismic information. This issue is important to Yucca Mountain hazard assessments because recent GPS data from Wernicke, et al. (2004) suggest significantly greater strain accumulation in and around Yucca Mountain than current estimates based on the geologic record that form the basis for current DOE seismic and volcanic hazard assessments. Several alternative explanations for the discrepancy between the geodetic and geologic strain rates were discussed. Transient Crustal Strain. Presentations on new GPS-derived displacement field data by B. Wernicke and GPS crustal models by K. Furlong suggest that geodetically-derived displacement data may reflect secular or time-transient behavior, perhaps related to post-seismic deformation within the earthquake cycle. In this explanation, the GPS data at Yucca Mountain record this short-term (10-100 yr) transient crustal strain. Such short term pulses would not impact the overall crustal strain patterns or hazard estimates because they are too short-lived to accumulate the necessary strains to generate or induce volcanism. Geodesists need to do additional work to determine the nature of this time transient behavior which may be relevant to considerations of deformation at Yucca Mountain.

4 Episodic Crustal Strain. The GPS data are recording an episodic pulse of increased strain accumulation. If the pulse duration is sufficiently long (on the order of 104 to 10 5 yrs) then enough strain could accumulate in the crust to generate earthquakes or induce volcanism. In this case the geologic record records the average between the active pulses and inter-pulse low activity. However, if the Yucca Mountain area is currently within one of these higher-activity pulses, then the GPS data, not the geologic data, may yield a more reliable estimate of the hazard activity. Undetected Geologic Strain. Comparisons between GPS displacement rates and fault displacement rates show a discrepancy between displacement rates measured by these two approaches. The GPS rates are accurate but the geologic rates underestimate actual deformation because the data only reflect that component of faulting and volcanism that is known. The discrepancy between the GPS and geologic rates can be accounted for in either non-seismogenic features (i.e., fractures, penetrative deformation, or fault creep) or in present but undetected faults and volcanic features. Additional geological data are needed concerning displacements and displacement gradients on mapped faults, as well as off-fault displacements (e.g., small scale faulting, extension fracturing, dike intrusion, grain scale deformation). GPS Uncertainty. There is significant disagreement among leading geodesists concerning treatment of error. Although assessments of formal error in GPS data acquisition appear to be similar among different groups, the University of Miami geodesy team includes additional sources of error such as monument instability in their analyses. These additional sources of error are not accounted by the Caltech/Harvard research team results. Correct interpretation of the GPS error is important to the recent GPS results reported for Yucca Mountain by Wernicke, et al. (2004) in which the Caltech/Harvard team showed an east to west increase in the rate of north-northwest directed displacement across Yucca Mountain and Crater Flat. These rates appear to be significantly larger than strains predicted using geologic information. Additional discussion at the meeting following a poster presented by the University of Miami team also showed that selection of an appropriate GPS reference frame is critical to the interpretation of the Yucca Mountain GPS data. Considering both the additional sources of uncertainty and reference frame issues, an independent analysis of the Yucca Mountain GPS data by the University of Miami team shows that reported displacements are uncertain. Nature and Style of Faulting Yucca Mountain is in the Walker Lane belt (Figure 1) which has geomorphic and tectonic characteristics consistent with characteristics of the Walker Lane. The tectonic setting of the Walker Lane is a topic of on-going geologic and geophysical investigations. At the Penrose Conference we heard emerging concepts of western North American tectonics that are benefitting from new surveying and computerized technologies that enable small horizontal and vertical components of motion to be observed, measured, and modeled. Results have been video-recorded and were displayed at the conference as time-scaled movies simulating plate tectonic motions.

The Walker Lane is an area of strike-slip deformation along the western margin of the . Although the western margin of the Walker Lane is consistently placed along the eastern margin of the Range, there was considerable variability in the map placement of the eastern margin of the Walker Lane. Although Stewart (1988) originally placed

5 the eastern edge of the Walker Lane along Las Vegas Valley, to include the Las Vegas Valley shear zone as part of the Walker Lane. Geodesists at the Penrose Conference generally placed the eastern margin of the Walker Lane along the eastern edge of the and Furnace Creek fault system. This definition is potentially important as it is related to Yucca Mountain, which is within the Walker Lane according to Stewart's definition, and outside of the Walker Lane according to the recent geodetic work. CNWRA work on faulting the Yucca Mountain region identified a strike-slip fault with apparent Quaternary displacement along the west side of Bare Mountain, on the Carrara fault. CNWRA staff consider this fault to represent the eastern margin of significant Quatemary strike slip of the Walker Lane.

There was considerable discussion at the conference concerning the possibility that the Walker Lane and Eastern California Shear Zone represent a nascent transform plate margin, that may ultimately localize itself within the Walker Lane, representing an eastward shift in the position of strike slip (transform) displacement between the Pacific and North American plates from its primary present day location along the . This interpretation is based on seismicity (e.g., Landers and Hector Mine earthquakes), geologically derived fault slip rates, and geodetically derived displacement (velocity) fields. If this interpretation were correct, and if the new transform plate margin localized itself along the eastern margin of the geodetically inferred Walker Lane, then the active plate margin would be as close as 50 km to Yucca Mountain.

SUMMARY OF ACTIVITIES:

D. Ferrill presented a poster on "Fission track constraints on external faulting and exhumation in the Walker Lane of southwestern Nevada and eastern California, U.S.A." P. Justus presented a poster on "Tectonic models relevant to potential tectonic hazards at proposed radioactive waste repository, Yucca Mountain, Nevada." J. Stamatakos presented two posters on the "Geologic record of Cenozoic extension in the Yucca Mountain area."

Staff also participated in the one-day field trip to observe fault slip transfer and characteristics of faulting on strike-slip and normal faults in the Eastern California Shear Zone and Walker Lane in California and Nevada. Field trips focused on active tectonic and geomorphic features in the between the Sierra Nevada frontal fault zone and the White Mountains fault zone.

CONCLUSIONS: The Penrose conference was a worthwhile source of up-to-date information on the tectonic setting of the southern Great Basin, including Yucca Mountain. Staff gained a clearer understanding of the natural hazards probabilities that are relevant to radioactive waste. The Penrose Conference was a worthwhile forum for informing the geologic and geophysical community of some of the U.S. NRC's investigations of the Yucca Mountain tectonics, particularly of faulting, tectonic setting of Yucca Mountain. In this way, the CNWRA and Headquarters participants functioned in an outreach mode that increased the understanding of the NRC and CNWRA role and function as an independent regulatory team by those who interacted with us during the Conference.

PROBLEMS ENCOUNTERED:

None

6 PENDING ACTIONS:

None

RECOMMENDATIONS:

Staff need to remain cognizant of the kinematics and geodynamics of the emerging technical developments concerning Eastern California Shear Zone and Walker Lane, as they may be applied to understanding and evaluating tectonic hazards at nuclear facilities in the western United States.

POINTS FOR COMMISSION CONSIDERATION:

No specific Commission consideration or action is needed.

ATTACHMENTS: Meeting Participants Roster

REFERENCES:

Stewart, J.H. "Tectonic of the Walker Lane Belt, Western Great Basin - Mesozoic and Cenozoic Deformation in a Zone of Shear." Metamorphism and Crustal Evolution of the Western United States, Vol. VII. W.G. Ernst, ed. Englewood Cliffs, New Jersey: Prentice-Hall, Inc. pp. 684-713.1988.

Wernicke, B., J.L. Davis, R.A. Bennett, J.E. Normandeau, A.M. Friedrich, and N.A. Niemi. "Tectonic Implications of a Dense Continuous GPS Velocity Field at Yucca Mountain, Nevada." Journal of Geophysical Research. Vol. 109, B12404. doi: 10.1029/2003JB002832. 2004.

7 JUN-16-2005 16:26 P. 02/03

SIGNATURES:

Philip S.Juft Dat Senior Geol"dw tIql RS. U.S. NRC

John A. Stamatakos Date Section Manager, CNWRA

David A. Ferrill Date Director, DEMPS

CONCURRENCE:

Jack Guttmann Date Section Chief, DHLWRS

Gordon Wittmeyer Date Assistant Director, CNWRA

Budh] Sagar Date President, CNWRA

8 - -

SIGNATURES:

Philip S. Justus Date Senior Gedol i L4WRS, U.S. NRC

6Dat4,e Jo tamatakos Date Section Manager, CNWRA

avid A. Ferrill ; U Date Director, DEMPS

CONCURRENCE:

Jack Guttmann Date Section Chief, DHLWRS

/2'/ Gordon Wittmeyer Date Assistant Director, CNWRA

DaIb1J"Je

8 Attachment

Meeting Roster for 2005 Penrose Conference

2005 Penrose Mammoth Lakes California (OSPENROSEi)

Dr. X Ernest Anderson Ooa37e K nt CA 93235-7 Thomas I. Andersoll U*Pk q* (412) 624-37 uopited Devt Geoloxy & eScienceiv 200Sp.ce Reeucb Cod Pibbu3ILPA 15260-37 Dr. Joseph E. Andrew YoWr uSmk Unieenky (33M 9414382 j1e ey13& GeoMhbadunlL S&dve one U qwAsiayaa YoguoWaMVH44555-V0I Dr.TanyaM Atwtr UkCa~ifi -Sa ba V3W5)893-4483 e o

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Dr. James Erew aBwftawwtrojoo l7aulds 91 x77xl -j wOmr IUiv Nevada - Rem .PS 178 AtnO. NV.895574001 Dr. LA Ferranti .Lm.o . Mt 10 39-971-474-426 IfenA6n hgoft N-W 50138 rI'ALY Dr. David A. Ferrill Soiiwehi Ps6arch [idbti(210)52Z2662 dawvld lsuig Caid NwciWaAte RnM Aniyiab 6220 QCkbr Rd StnAioo, TX 12385166 Dr. Robert C. Finkel Itwr e Lvam6w NafiomnLab (925)422-2044 finkellOlngV CAM 7000 stAVe

David M. Fountain Naiona ScienwceTowation (703) 2924751 dfttdtaiOmnsov Ewrth-SciemCea Vivision- Itm 785 4201 Wil8qn]3vd Adio VA =2201 Kurt L Frankel UnIv. of outhem Cifornmi (213)7404208 kfit"G@scedu DepctfEazthSlencesWZ S 117 3651 rQuesdaleky. Lo Aeles CA 0740 Prof.AnkeXMFzedrkh U im +4M9-51-762-228 ftkdkhGeowLud-h lmnst itut~~teolo~ei caffihw. H ver.Medenacbsta 30167

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10 A, =ES PHON Bum Prof. John W. Gelsman UnivNeLexico (505)'277-3433 jgelsstmnech 203NoftbkoI,--a- AluuerqueNM 87131-001

AMen F. Glazner Univ Noth Cara= - chape Hl (919)92-8 afgunc8edu

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5805 FoNtaisauDe NcwOdeanS.A70125-34S8 Dr. Joh A. Stamatakos *Southwest Rearch Istute (210)522-5247 jstitwta Cnta NuclerWaWs Ret Anfth TOBD1x28510 .San Azto, TX78220510 Dr. Daniel F. Stoi univKus - (7)8644995 MCkH sL Dept GrebIr 120 lbdleyHall 1475 JAylawit BId LAwiece, KS 66045.7613 Mr. anrdel M Stotmer 400MnraLoar.Apt#242 (77)4-691xlxi dwzriCjvada Ren,. NV 89302 Ms. Tatia IL Taylor Univ CaifMOnli -Daiis (530)752-0350 teopogy.M 174 PhnsclGalb Davs, CA 95616 ,. Mr. Christopher IL Theher 913 MinIls )864m7713 twberkLedo _iwecc, XS 66044 Dr. Paul J. Umheoder Nordm Au= Univ (98J523-6464 piu.efne u.ec Dept Geoloxy POBox4099 V&Sast&t. A"Z$d!-011 lDougit Walker Uiv Kinso (785)3642735 jdvinanrakue Dept Ceolony- 126 Llmdleylrbb 1475 Jayhaw~tBlvd LAtWKS6045-7613 Brihn P. Wernkke Calonlia InsideTecaoloy (626) 3-192 bd=gps.cad edu Div ceolodal i&PlaenWcOe_ 1201 E Cefifom!i Blvd MC 100-23 P*Mdm CA 91125W001

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