State of Practice Approaches in Geomorphology ......State of Practice Approaches in Geomorphology,...

Presentation to Department of Energy

Natural Phenomena Hazards Meeting

October 21-22, 2014

State of Practice Approaches in Geomorphology, Geochronology

and Probabilistic Analyses for Addressing Fault Capability at

Nuclear Facilities

Click to edit Master title style

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Overview

• Case history on application of state of practice site characterization investigations for assessing the suitability of two sites for a proposed second nuclear power plant (NPP) at Krško, Slovenia • Site Characterization investigations to evaluate capability of

faults within 5 km of planned NPP sites (2) • PFDHA conducted to assist utility in making informed

decision on suitability of proposed NPP sites with respect to the probability of surface fault displacement


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Overview

• Site characterization investigations follow IAEA SSG-9 guidance include • Tectonic geomorphic analyses related to landscape

evolution • Geochronology based on multiple methods for constraints on

faulting • High resolution seismic (refraction & reflection) surveys to

identify extent of faulting in site vicinity • Probabilistic evaluation of fault displacement hazard to

support • Utility in assessing nuclear safety • Regulatory decision-making following IAEA SSG-9

• Focus of investigations on Libna Fault that is mapped in close proximity to proposed eastern NPP site


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BACKGROUND

• Krško, Slovenia is located in southeastern Slovenia in an area defined by a triple junction between the Alps, Dinarides, and the Pannonian Basin • Region is within the transition zone between the Sava Folds and

the southeastern extension of the Mid-Hungarian Shear Zone • Region of moderate seismicity

• Paleoseismic investigations conducted prior to 2012 demonstrated the Libna Fault to be: • Capable based on age • within 1-2 km of the existing proposed sites for Krško NPP 2


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Background (Cont’d.)

• Utility and expert reviewer questioned the interpretation of the Libna Fault’s capability by previous investigators based on: • Questionable optical stimulated luminescense (OSL) ages

(possible at saturation limits – i.e. the maximum age capacity)

• Inferred projections of the Libna and other faults • Judgments made based on limited, and potentially unreliable

data


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Tectonic Framework of Adriatic Microplate transition zone at northern extent of Mid Hungarian Shear Zone


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Sites Libna Flt

Approximate Lineament Map surrounding the Krško Basin


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Trench Excavated Across Libna Fault

From GeoZS 2013

Trench excavated in high-density, karst landscape -- brings into question the mode of recent displacement

Trench wall faces south


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Trench map of notable Karstic dissolution features


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LiDAR DEM

Deep-seated landslide provides local analog for ‘exaggeration’ of the Libna Feature – site located ~12 km from Libna Trench Extensive karst is common to region (note the sinkholes) Note difference between 1m LiDAR DEM and conventional 5m resolution DEM

1m DEM 5m DEM


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Lineament map Based on DEM derivatives


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Libna Hill Morphology

Signatures of: • Faulting? • Landsliding? • Karst?


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3D oblique images


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Enhanced LiDAR DEM showing location of trench relative to karst and landsliding Apparent continuity in SE corner is a fluvial scarp – proven with additional trenching Indicating

location of trench Fluvial scarp


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High Resolution Seismic Survey

• Seismic survey designed to explore extension of the Libna fault in the Krško basin

• Used high resolution refraction & reflection approach designed for identifying near surface features

• Develop hybrid, diving wave refraction tomography for additional near-surface characterization

• Faults were identified but no faulting observed in the upper Miocene marls • Marl underlie young valley fill (10-120m) • Dip direction of faults identified in HRS survey tend to have dip

direction opposite that of the Libna fault • Suggests a lack of fault continuity


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Plan View Showing Possible Faults


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Krsko Basin Sediments

OSL sediment “depositional” ages • CRN elevation

(322 m) ~1.8 Ma • Libna Trench

(140 ka) (315-320 m) elevation

• OSL elevations

(150-215) m


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Conceptual capacity of OSL in the Krsko Basin

All other age dates

CRN date

OSL date


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Quaternary Aggradation and Incision Scenarios

To accept the Libna Trench OSL age, there are two scenarios necessary: • Catastrophic aggradation of Sava River: greater than 100m/

1,000 years

• Catastrophic incision of Sava River: greater than 100m/1,000 years

*There is no evidence for any catastrohic events that occurred in the region that could have led to either of these scenarios

• Moderate incision of Sava River (0.09m/1,000 years) this is consistent with incision rates of the southern Alps

• Suggests provides a more representative age than the Libna Trench OSL age.

Long term = 0.09m ka-1


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Findings of Geomorphic, Geophysical and Geochronology Investigations Investigations

• Libna Hill and surrounding area is dominated by karst and landsliding

• Apparent offset of the Globoko Fm. May be greatly exaggerated by karst and landsliding

• CRN analyses suggests age of Globoko Fm. Is approximately same as published interpretations

• Use of OSL may be limited to dating sediments around 200Ka in the region (not unusual for OSL limitations)

• Libna fault, if displacement of Globoko is tectonic has an age of less than 1.7 Ma

• Libna fault may be discontinuous within the Miocene bedrock with a maximum length of 1.5 to 4.5 km


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PFDHA

• Methodology: Petersen et al. (2011) • Extension of “earthquake” approach developed by

Youngs et al. (2003) for the Yucca Mountain Project

• Treats on-fault and off-fault displacement • Uses Petersen et al. fault displacement data base • Accounts for uncertainty related to fault mapped location

accuracy & fault complexity


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Key PFDHA Inputs

• Probability of activity • Fault length • Fault location • Slip rate • Maximum magnitude • Hazard calculation cell size • Fault location uncertainty (mapping accuracy

and fault complexity)


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Fault Model

45.85

45.95

46.05

15.4 15.5 15.5 15.6 15.6 15.7 15.7 15.8 15.8

Latit

ude

(Deg

N)

Longitude (Deg E)

Libna Gabrnica

Gorica

Sromljica

Stara Vas

Mocnik 1

Mocnik 2

Orlica N

Orlica S


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Krško PFDHA Results

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

0.001 0.01 0.1 1 10

Mea

n A

nnua

l Fre

quen

cy o

f Exc

eeda

nce

Displacement (m)

East SiteWest Site

Total Hazard


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Fault Source Contribution-East Site

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

0.001 0.01 0.1 1 10

Mea

n A

nnua

l Fre

quen

cy o

f Exc

eeda

nce

Displacement (m)

Total hazard Artice_Extended_East Artice_Extended_West Artice_LongArtice_Short Gabrnica_A Gabrnica_B Gorica_AGorica_B Hrastnik Libna_A Libna_BLibna_C Mocnik_1 Mocnik_2a Mocnik_2bOrlica_North Orlica_South Sromljica_A Sromljica_BStara_Vas_A Stara_Vas_B

Orlica South

Stara Vas B

Libna A & B

East Site

Source: RIZZO (2013a, Figure 14)


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PFDHA Findings

• Petersen et al. methodology is appropriate for PFDHA application in the geologic setting of Krško

• The probability of exceeding surface displacement values of about 5 cm or greater at the Krško East and West Sites is very low: about 10-8 or less

• Libna fault does not pose a suitability issue for either sites

• This finding also applies to the existing Krško 1 NPP Site


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Conclusions

• Tectonic geomorphic and landscape evolution methods should be applied, that rely on multiple age dating methods and high resolution topography. Combined, these methods allow for a broader understanding of the processes that shape the landscape, including faulting, karstic dissolution, landsliding and fluvial erosion.

• PFDHA has had limited application in assessing suitability of existing and proposed NPP sites; however, its application has been beneficial to aiding decision makers in assessing site suitability.


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Contact Information

• K. Michael Cline – [email protected] • M. Logan Cline –

[email protected] • Richard Quittmeyer –

[email protected]

State of Practice Approaches in Geomorphology ......State of Practice Approaches in Geomorphology,...

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