HomeMy WebLinkAboutDRC-2015-002242 - 0901a06880523f85DRC-2015-002242
Energy Fuels Resources
(USA) Inc.
WHITE MESA MILL
@) MWH
BUILDING A BETTER WOULD
3665 JFK Parkway
Suite 206
Fort Collins, CO USA
Probabilistic Seismic Hazard
Analysis
MafGh-April 2015
Probabilistic Seismic Hazard Analysis
Energy Fuels Resources (USA) Inc. MWH Americas, Inc.
i March April 2015
TABLE OF CONTENTS
1.0 INTRODUCTION ............................................................................................................... 1
1.1 Background and Purpose ...................................................................................... 1
1.2 Approach ............................................................................................................... 1
1.3 Design Criteria ....................................................................................................... 2
2.0 GEOLOGIC SETTING ...................................................................................................... 3
2.1 Regional Setting .................................................................................................... 3
2.2 Site Geology .......................................................................................................... 3
3.0 SEISMOTECTONIC SETTING AND HISTORICAL SEISMICITY .................................... 4
3.1 Historical Seismicity .............................................................................................. 4
3.2 Catalogs of Earthquake Data ................................................................................ 4
3.2.1 Petersen Catalog ....................................................................................... 4
3.2.2 ComCat...................................................................................................... 4
3.2.3 Combined Catalog and Magnitude Bias Correction ................................... 5
3.2.4 Earthquakes Attributed to Specific Faults .................................................. 5
3.2.5 Artificially Induced Earthquakes ................................................................. 5
3.3 Magnitude Conversion .......................................................................................... 5
3.4 Developing Recurrence Parameters ..................................................................... 6
3.4.1 Assessment of Catalog Completeness ...................................................... 6
3.4.2 Estimation of the Recurrence Parameters ................................................. 7
4.0 SEISMIC SOURCE CHARACTERIZATION ..................................................................... 8
4.1 Faults ..................................................................................................................... 8
4.1.1 Capable Faults........................................................................................... 8
4.1.2 Fault Sources............................................................................................. 8
4.2 Seismic Sources .................................................................................................... 9
4.2.1 Colorado Plateau ..................................................................................... 10
4.2.2 Intermountain Seismic Belt ...................................................................... 11
4.3 Shear Wave Velocity ........................................................................................... 11
4.3.1 Summary of Site-Specific Vp Values ........................................................ 11
4.3.2 Development of Vp/Vs Ratio .................................................................... 12
4.3.3 Estimation of Site-Specific Vs Values ...................................................... 14
5.0 GROUND MOTION PREDICTION EQUATIONS ........................................................... 16
6.0 PROBABILISTIC SEISMIC HAZARD ANALYSIS ......................................................... 17
6.1 PSHA Code and Methodology............................................................................. 17
6.2 PSHA Inputs ........................................................................................................ 17
6.2.1 Areal Source Zones ................................................................................. 18
6.2.2 Fault Sources........................................................................................... 18
6.3 Probabilistic Seismic Hazard Analysis Results .................................................... 18
7.0 RESULTS AND COMPARISON WITH PREVIOUS STUDIES ....................................... 20
8.0 REFERENCES ............................................................................................................ 2221
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LIST OF TABLES
Table 1. Time Periods for Complete Event Reporting ................................................................. 6
Table 2. Colorado Plateau – Magnitude Bins and Cumulative N* Values ................................... 7
Table 3. Intermountain Seismic Belt– Magnitude Bins and Cumulative N* Values ..................... 7
Table 4. Minimum Criteria for Faults Considered in Seismic Investigation (NRC 10
CFR Appendix A to Part 100) ..................................................................................... 8
Table 5. Envelope of Vp and Vs Values for the White Mesa Site ............................................... 15
Table 6. GMPEs used in the PSHA ........................................................................................... 16
Table 7. PSHA Input Parameters ............................................................................................... 17
Table 8. PSHA Results .............................................................................................................. 18
LIST OF FIGURES
Figure 1 Quaternary Faults Within the Study Area
Figure 2 Faults and Earthquake Events Included in PSHA
Figure 3 Catalog Completeness Plots
Figure 4 Areal Source Zones
Figure 5 Gutenberg-Richter Relationship, Colorado Plateau
Figure 6 Gutenberg-Richter Relationship, Intermountain Seismic Belt
Figure 7 Seismic Refraction Data and Boring Locations
Figure 8 Fault Traces as Modeled in the PSHA
Figure 9 Peak Ground Acceleration Seismic Source Contribution
Figure 10 VS30 Peak Ground Acceleration Seismic Source ContributionUniform Hazard
Spectra Comparison of VS30
Figure 11 Deaggregation of PGA 10,000-Year Return Period for VS30=580m/s
Figure 12 Deaggregation of PGA 10,000-Year Return Period for VS30=940m/s
Figure 13 Deaggregation of PGA 10,000-Year Return Period for VS30=1,190m/s
LIST OF ATTACHMENTS
Attachment 1 List of Earthquake Events within the White Mesa Study Area
Attachment 2 List of Faults and Fault Characteristics Included in the PSHA
Attachment 3 Summary of Individual Fault Parameters
Attachment 4 Dames & Moore Boring Logs (1978)
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1.0 INTRODUCTION
This report presents results of a site-specific probabilistic seismic hazard analysis (PSHA) to
develop the seismic design criteria for reclamation of the White Mesa Mill (site). The site is
approximately 6 miles (10 km) south of Blanding, Utah at approximately 37.5° N latitude and
109.5° W longitude. Site facilities consist of a uranium processing mill and five lined
tailings/process solution storage cells located within an approximately 686-acre restricted area.
The probabilistic seismic hazard analysis is based on a seismotectonic model and source
characterization of the site and surrounding area. The study evaluated a 200-mile (322-km)
radius surrounding the site. For purposes of this report, this area is termed the “study area”
(Figure 1).
The seismotectonic model identified three general seismic sources in the study area: 1)
seismicity of the Intermountain Seismic Belt (ISB), 2) seismicity of the Colorado Plateau (CP),
and 3) crustal faults that meet the NRC minimum criteria discussed in Section 4.1.1. Each
source zone was characterized to establish input parameters for the seismic hazard analyses.
The PSHA was performed using HAZ43 (2014) software developed by Dr. Norman
Abrahamson. Operational and long-term design recommendations were developed based on
the results from this PSHA and previous seismic investigations at the site.
1.1 Background and Purpose
The Utah Division of Radiation Control (DRC) requested that Energy Fuels Resources (USA),
Inc. (EFRI) conduct a site-specific PSHA for reclamation of the site. This request was part of
DRC’s February 2013 review comments (DRC, 2013) on EFRI’s August 2012 responses to
DRC’s Round 1 interrogatories for the White Mesa Reclamation Plan Rev. 5.0 (EFRI, 2012).
The PSHA was performed to estimate the seismic hazard at the project site within a probabilistic
framework by characterizing potential seismic sources. better understand the likelihood of the
potential earthquake sources, to correlate results with previous analyses conducted for the site,
and to evaluate the contribution of the seismic sources (e.g. deaggregation). This analysis
assessed the site-specific seismic hazard using Ground Motion Prediction Equations (GMPEs)
to estimate seismically induced ground motions at the site. Seismic hazard analyses were
previously conducted for the design of the Cell 4A and 4B facilities (MFG, 2006; Tetra Tech,
2010) and in response to DRC review of EFRI responses to interrogatories on the Reclamation
Plan (MWH, 2012). These analyses indicated that the seismic hazard at the site is dominated by
background events in the Colorado Plateau.
This report presents a description and results of analyses conducted to respond to the DRC’s
comment on ERFI’s interrogatory responses (DRC, 2013) requesting a site-specific seismic
hazard evaluation be performed to develop site-specific seismic design parameters. This report
also addresses comments later provided by URS (URS, 2015; URS, 2015b) in response to a
previous versions of this report. This report has been prepared by MWH Americas, Inc. (MWH)
at the request of EFRI.
1.2 Approach
This evaluation used data on faults and earthquakes occurring within a 200-mile (322-km)
radius of the site to develop seismic source characterization for the PSHA. An earthquake
catalog was compiled and the historical seismicity and information on specific faults was used to
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develop the seismic source models for the three seismic sources described above. The PSHA
considered all defined seismic sources with the goal of identifying the major contributor(s) to the
seismic hazard at the site. The hazard is defined according to GMPEs selected for the region.
1.3 Design Criteria
The design life for the reclaimed facility is required to be 1,000 years to the extent reasonably
achievable, and at least 200 years, per the US Environmental Protection Agency (EPA) (EPA 40
CFR 192) and the US Nuclear Regulatory Commission (NRC) (NRC 10 CFR Appendix A to Part
100 A) (NRC, 2013). An event with a 10,000-year return period has a 2 percent probability of
exceedance during a 200-year period and a less than 10 percent probability of exceedance in a
1,000-year period. Therefore, the peak ground acceleration (PGA) calculated using a 10,000-
year return period is conservative, but appropriate for the reclaimed (long-term) seismic design
criteria for the site.
The peak ground acceleration calculated in this PSHA will be used during reclamation design to
evaluate liquefaction potential and slope stability of the reclaimed tailings cells. These analyses
use either the PGA or a pseudostatic coefficient of 2/3 of the PGA (DOE, 1989).
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2.0 GEOLOGIC SETTING
2.1 Regional Setting
The Reclamation Plan for White Mesa Mill (Denison, 2011), and previous seismic studies
(MWH, 2006; Tetra Tech, 2010) provide information on the regional geologic setting. Only
information relevant to the PSHA will be included here.
The site is located within the Colorado Plateau physiographic province in southeastern Utah.
The Colorado Plateau is a broad, roughly circular region of relative structural stability. The
contemporary seismicity of the Colorado Plateau was investigated by Wong and Humphrey
(1989), based on seismic monitoring. Their study characterized seismicity of the plateau as
small to moderate magnitude with a low to moderate rate of widely-distributed earthquakes with
hypocentral depths of 9 to 12 miles (15 to 20 km). The area is characterized by generally
northwest-striking normal faulting.
Regional geology approximately 50 to 100 miles (80 to 161 km) north to northeast of the site is
characterized by the Uncompahgre Uplift and salt tectonics of the Paradox Valley area. The
Uncompahgre Uplift is a northwest-trending, east-tilted fault block located in southwest
Colorado. For purposes of this PSHA, faults associated with the Uncompahgre Uplift are
considered seismogenic. Faults in the area of the Paradox Valley are generally related to salt
tectonics and are considered non-seismogenic.
The western extent of the study area is bounded by the eastern extent of the Intermountain
Seismic Belt (ISB). The ISB runs from northwestern Montana south into northern Arizona and is
one of the most extensive zones of seismicity within the continental United States (Wong et al.,
1997). Much of the ISB near the site is characterized by north-trending normal faults. The two
largest earthquakes recorded in the study area, moment magnitude (Mw) 6.0 and 6.5, occurred
within the ISB.
The southern and southeastern extent of the study area is a relatively stable area of the
Colorado Plateau with no Quaternary faults. One exception is the Northern Nacimiento fault,
located in northeastern northwestern New Mexico.
2.2 Site Geology
Information on site geology is provided in the Reclamation Plan for the White Mesa Mill
(Denison, 2011). This information is summarized below.
The site is located near the center of the White Mesa in southeastern Utah. The area is a north-
south trending mesa characterized by steep canyons formed by stream erosion. The site is
underlain by the Dakota Sandstone, predominately composed of cross-bedded, fine- to coarse-
grained, well-cemented sand (Denison, 2011). Site soils are predominantly derived from wind-
blown sediment. In the area of the tailings cells, soils were removed during construction, as
discussed in Section 4.3.1.
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3.0 SEISMOTECTONIC SETTING AND HISTORICAL SEISMICITY
3.1 Historical Seismicity
The seismic hazard analysis for the site includes a review of historic earthquakes within the
study area. The historic earthquake record for the study area contains earthquakes from 1887
through the end of 2014 and provides a general overview of the seismicity of the study area.
Figure 2 shows seismicity [events with moment magnitude (Mw) greater than or equal to 3.0 (Mw
≥ 3.0)] within the study area. The earliest recorded event included in the final PSHA catalog
occurred in 1887. The PSHA catalog contains two events larger than or equal to moment
magnitude 6.0 (Mw ≥ 6.0) and 11 events with moment magnitudes greater than or equal to 5 and
less than 6 (6 > Mw ≥ 5). The remaining events are all less than Mw 5.0 (Mw < 5). All events
described in this report are given in moment magnitude unless specified otherwise.
The following paragraphs summarize development of the earthquake catalog used in the PSHA.
3.2 Catalogs of Earthquake Data
3.2.1 Petersen Catalog
Catalogs from the US Geological Survey (USGS) NSHMP for the Western United States (WUS)
and Central and Eastern United States (CEUS) (Petersen et al., 2014) were used to compile
information regarding historic earthquakes within 200 miles (322 km) of the site. Petersen et al.
(2014) compiled the catalogs for the WUS and CEUS by reviewing and combining other
available catalogs. Petersen et al. (2014) used their interpretation of catalog reliability to
eliminate duplicate records when earthquakes were listed in more than one catalog. Since
attenuation relations, completeness, and magnitude conversion rules all vary regionally,
Petersen et al. (2014) built two catalogs generally following the approach used by the CEUS-
SSCn (NRC et al., 2012): a catalog for WUS and a catalog for the CEUS. Petersen et al. (2014)
converted both catalogs to Mw from the original magnitude recorded.
Within the study area, the Petersen et al. (2014) database includes historical seismic events
from 1887 through 2012 for the WUS and events from 1910 through 2012 for the CEUS. Both
catalogs contain events with Mw ≥ 3.0. AutoCAD software was used to delineate a 200-mile
(322-km) radius around the site to identify only those events within the seismic study area.
Further steps taken to develop the final PSHA catalog are discussed below. The PSHA catalog
includes 328 events from the Petersen catalog.
3.2.2 ComCat
Earthquake information from the WUS and CEUS catalogs was supplemented by a search of
the Advanced National Seismic System (ANSS) Comprehensive Catalog (ComCat), also
maintained by the USGS. ComCat was used to obtain additional earthquake information from
January 1, 2013 through February 7, 2015. The catalog was accessed on February 8, 2015.
ComCat contains data from networks that contribute to the ANSS database as well as historical
data from the USGS National Earthquake Information Center’s (NEIC) Preliminary
Determination of Epicenters (PDE) catalog
(http://earthquake.usgs.gov/earthquakes/eqarchives/epic/). AutoCAD software was used to
delineate a 200-mile (322-km) radius around the site to identify only those events within the
seismic study area. The final catalog includes six ComCat events.
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The ComCat was declustered for this PSHA using the Reasenberg (1985) algorithm to remove
dependent events (aftershocks and foreshocks). In order to use the independence assumption
of a Poisson model (typically assumed in PSHA analyses), events that can be associated with
other close-in-time and near-in-space events must be removed from the catalog. Reasenberg’s
algorithm identifies events that occur within time and distance windows, termed clusters. These
clusters are then replaced with the mainshock.
3.2.3 Combined Catalog and Magnitude Bias Correction
The ComCat and Petersen catalogs were combined to create a final declustered catalog for the
PSHA. The Petersen catalog reports magnitude as expected moment magnitude E[MW]
(Petersen et al., 2014). The conversion of various magnitudes to E[Mw] for events from the
ComCat was completed following the guidance presented in CEUS-SSCn (NRC et al., 2012).
This approach is identical to that used in development of the Petersen catalog.
The PSHA catalog includes expected magnitude E[MW], magnitude uncertainty, and a counting
factor termed N* (or nstar) for each event. The counting factor N* was used to compute
unbiased earthquake rates following guidance presented in CEUS-SSCn (NRC et al., 2012).
Earthquake recurrence parameters were computed using the maximum likelihood approach by
using the N* factor instead of the observed counts. This approach has been shown to work well
for catalogs with variable levels of catalog completeness as a function of magnitude (CEUS-
SSCn, NRC et al., 2012).
3.2.4 Earthquakes Attributed to Specific Faults
In order to prevent double-counting earthquakes in both the fault and areal source models,
earthquakes occurring within 3.1 miles (5 km) of faults were evaluated in detail. Within the study
area, 31 events were located within 3.1 miles (5 km) of Quaternary faults. In order to evaluate
the difference between the earthquake recurrence parameters, the recurrence was computed
with and without these events. The result was very little variation in the a and b parameters with
or without the 31 events. Additionally, the recurrence calculations for the catalog including the
31 events resulted in an exponential distribution with a better fit to the data. Therefore, given the
small variation in results, and the fact that the literature indicates most earthquakes within the
CP (Wong and Humphrey, 1989) and ISB (dePolo, 1994) are not related to surface ruptures, all
earthquake events in the areal source zones were included in the recurrence calculations.
3.2.5 Artificially Induced Earthquakes
Several areas of artificially induced seismic activity are located within the study area. These
include: 1) an area between Glenwood Springs and Paonia, Colorado (Swanson et al., 2008,
and CGS, undated), 2) the Book Cliffs-eastern Wasatch Plateau area near Price, Utah (Arabasz
et al., 2005), and 3) the Paradox Valley area (Ake et al., 2005). The areas listed above were
examined against the Petersen catalog and were confirmed as having been removed from the
Petersen catalog. Furthermore, no events in the ComCat fall within these areas of artificially
induced seismicity.
3.3 Magnitude Conversion
All events described here are reported in moment magnitude unless specified otherwise. The
events included in the Petersen catalog were all given in Mw; therefore, it was only necessary to
convert those events from the ComCat. This conversion was completed by following the
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approach used to compile the Petersen catalog and guidance provided in CEUS-SSCn (NRC et
al., 2012).
The earthquake catalog used in the recurrence calculations for this PSHA includes the
combined Petersen et al. (2014) catalog and ComCat. The data was declustered and screened
to exclude artificially-induced earthquakes due to anthropogenic activity. The final catalog used
for the PSHA includes 334 earthquakes. These earthquakes are shown on Figure 2.
Earthquakes included in the final catalog for the computation of recurrence parameters
generally have small magnitudes, with over 90 percent of the earthquakes having a Mw < 5.0.
Figure 2 shows that earthquake activity within a 200-mile (322-km) radius of the site is diffuse,
with the exception of those in the ISB located on the western edge of the study area, and in
western Colorado (the northeast corner of the study area). A list of historical earthquakes is
included in Attachment 1.
3.4 Developing Recurrence Parameters
To estimate probabilistic ground motions for the site, recurrence parameters are required to
characterize seismic activity in the study area. Two areal source zones were delineated within
the study area, as discussed in Section 4.2.
3.4.1 Assessment of Catalog Completeness
In order to estimate a recurrence rate for earthquakes, an assessment of the completeness of
the earthquake catalog was necessary. One way to test completeness is to plot the rate of the
earthquakes (number of events greater than a specified magnitude divided by the time period)
as a function of time, starting at present time and moving back towards the beginning of the
catalog. If the rate of earthquakes is represented by a stationary Poisson process (the rate -m-
does not change with time) for the study area, which is the typical assumption, then the rate of
earthquakes should remain constant for the portions of the catalog that have complete
reporting.
The evaluation was performed using the Stepp (1972) method, which includes generating
completeness plots to visually inspect the rate of events over the years. Plots were developed
starting at a minimum magnitude of 3.0 and carried out for each 0.5 to 1.0 magnitude unit,
depending on the size of the magnitude bins. Based on this evaluation, the catalog is
considered complete for the date and magnitude ranges shown in Table 1. Figure 3 shows the
catalog completeness plots developed for this study.
The catalog is complete for those events greater than Mw 5.5 for approximately 130 years, this
corresponds to the 1880’s, when settlement became more widespread for southeastern Utah.
The first event in the catalog is a Mw 5.7 which occurred in 1887.
Table 1. Time Periods for Complete Event Reporting
Magnitude Range Period of Complete
Reporting
3≤M<3.5 1984 2014
3.5≤M<4.0 1964 2014
4.0≤M<4.5 1964 2014
4.5≤M<5.0 1959 2014
5.0≤M<5.5 1904 2014
M≥5.5 1884 2014
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3.4.2 Estimation of the Recurrence Parameters
After the completeness intervals for each magnitude range were developed and dependent
events were removed, the recurrence parameters were computed. A common way to
characterize this frequency is by using the Gutenberg-Richter relationship, which is linear when
the magnitude is plotted against the frequency of events on a semi-logarithmic scale. The
magnitude-frequency relation expressed in its cumulative form is:
logܰሺܯሻ ൌܽെܾܯ
where M is the magnitude and N is the cumulative frequency of earthquakes greater than
magnitude M. The calculation of cumulative frequency of earthquakes (N) used the N* value (a
counting factor used to compute unbiased rates) instead of observed counts. Recurrence
relationships were then estimated using the maximum likelihood procedure developed by
Weichert (1980). The maximum likelihood line is characterized by the slope of the line, or b-
value, and the log N value at a magnitude of zero (a-value). For this study, a minimum
magnitude of 3.0 was used to develop the recurrence parameters. The inputs used to calculate
the recurrence parameters are summarized in Table 2 and Table 3. The recurrence parameters
(a- and b-values) were developed for each seismic source zone, as discussed in Section 4.2.
Table 2. Colorado Plateau – Magnitude Bins and Cumulative N* Values
Magnitude Bin Cumulative N* value Cumulative Observed
Counts
3≤M<3.5 78.59 69
3.5≤M<4.0 52.65 46
4.0≤M<4.5 18.25 16
4.5≤M<5.0 8.03 7
5.0≤M<5.5 4.82 4
5.5≤M<6.0 1.21 1
Table 3. Intermountain Seismic Belt– Magnitude Bins and Cumulative N* Values
Magnitude Bins Cumulative N* value Cumulative Observed
Counts
3≤M<3.5 136.51 133
3.5≤M<4.0 81.48 78
4.0≤M<4.5 32.56 31
4.5≤M<5.0 14.89 14
5.0≤M<5.5 7.98 7
5.5≤M<6.0 4.71 4
6.0≤M<6.5 2.41 2
6.5≤M≤7.0 1.21 1
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4.0 SEISMIC SOURCE CHARACTERIZATION
The seismic source model includes crustal fault sources, seismicity of the ISB, and seismicity of
the Colorado Plateau (CP). These sources are described below.
4.1 Faults
4.1.1 Capable Faults
A “capable fault” is defined by the Nuclear Regulatory Commission (NRC) in 10 CFR Appendix
A to Part 100, Seismic and Geologic Siting Criteria for Nuclear Power Plants, as a fault that has
exhibited one or more of the following characteristics:
1. Movement at or near the ground surface at least once within the past 35,000 years or
movement of a recurring nature within the past 500,000 years.
2. Macro-seismicity (magnitude 3.5 or greater) instrumentally determined with records of
sufficient precision to demonstrate a direct relationship with the fault.
3. A structural relationship to a capable fault according to characteristics (1) or (2) above
such that movement on one could be reasonably expected to be accompanied by
movement on the other.
Capable faults must also meet the minimum criteria for fault length and distance from the site,
as defined by NRC 10 CFR Appendix A to Part 100, and included in Table 4. A fault that is
deemed capable by the criteria listed above, but does not meet the minimum criteria provided in
Table 4, does not need to be considered in the seismic hazard analysis.
The term “capable fault” may be abandoned by the NRC, but this is not yet reflected in the CFR,
so the term is used in this report.
Table 4. Minimum Criteria for Faults Considered in Seismic Investigation (NRC 10 CFR
Appendix A to Part 100)
Distance from Site
(mi)
Minimum Length of Fault to be
Considered
(mi)
0 to 20 1
20 to 50 5
50 to 100 10
100 to 150 20
150 to 200 40
All capable faults that meet the minimum criteria presented above were considered in the
PSHA.
4.1.2 Fault Sources
The existence and location of faults with Quaternary displacement were primarily identified
using the USGS Quaternary Fault and Fold database (USGS et al., 2013). All faults identified
with potential Quaternary-age offset that exist within a 200-mile (322-km) radius of the site are
shown in Figure 1. Those faults were further screened to those that meet the criteria listed in
Table 4 and shown in Figure 2.
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All faults that meet the requirements outlined in Table 4 were considered in this seismic
investigation. This is a conservative approach, because although the NRC defines a “capable
fault” as one having “movement at or near the ground surface at least once within the past
35,000 years or movement of a recurring nature within the past 500,000 years,” including all
identifiable faults with Quaternary displacement would include fault movement over the past 1.8
million years. The 41 faults considered in the seismic hazard analysis are listed in
Attachment 2.
The USGS separates faults with Quaternary displacement into classes. These classes are
provided below, as described by USGS et al. (2013).
For a Class A fault, geologic evidence demonstrates the existence of a Quaternary fault
of tectonic origin, whether the fault is exposed by mapping or inferred from liquefaction
or other deformational features.
For a Class B fault, geologic evidence demonstrates the existence of Quaternary
deformation, but either 1) the fault might not extend deeply enough to be a potential
source of significant earthquakes, or 2) the currently available geologic evidence is too
strong to confidently assign the feature to Class C but not strong enough to assign it to
Class A.
For a Class C fault, geologic evidence is insufficient to demonstrate 1) the existence of
tectonic faulting, or 2) Quaternary slip or deformation associated with the feature.
For a Class D fault, geologic evidence demonstrates that the feature is not a tectonic
fault or feature; this category includes features such as joints, landslides, erosional or
fluvial scarps, or other landforms resembling fault scarps but of demonstrable non-
tectonic origin.
The faults with Quaternary displacement that meet the NRC minimum criteria and are included
in this analysis are either Class A or B.
Many of the faults in Colorado are attributed to the Uncompahgre Uplift. The Uncompahgre
Uplift faults are typically northwest-trending normal faults with minimal evidence to constrain the
slip rates. Faults located north of the site in the area of the Paradox Valley are associated with
salt tectonics and are therefore considered non-seismogenic. Faults in the western section of
the study area are assumed to be seismogenic. Tectonic features in this area include Basin
and Range extension, multiple small-scale mountains and plateaus, and the southern extent of
the Wasatch Plateau in central Utah.
Characteristics of individual faults that meet the criteria specified in Table 4, including
subsurface orientation, depth, slip rate, probability of activity, and age were obtained where
possible from USGS et al. (2013), Wong et al. (1989 and 1996), and Hecker (1993). A
comprehensive list of fault characteristics used in the PSHA is included in Attachment 2 and
Attachment 3. Published fault characteristics were used when available. When there were no
published sources for specific faults, a weighted range of values were used. The probability of
activity is the probability that a fault is seismogenic. For purposes of this analysis, non-
seismogenic faults were assigned a value of probability of activity of 0.5 or less and
seismogenic faults are assigned a probability activity of 1.0.
4.2 Seismic Sources
The hazard from background events unassociated with known faults was assessed by dividing
the area of the 200-mile (322-km) radius around the site into two areal source zones that were
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assessed independently. The first zone is a portion of the Intermountain Seismic Belt (ISB),
discussed previously in Section 2.1. This area includes the western portion of the study area,
as shown in Figure 4. The second areal source zone is the Colorado Plateau (CP), and includes
the remaining portion of the study area, as shown in Figure 4. The CP is characterized by a
dispersed distribution of historic seismic events, and the ISB is characterized by a denser
distribution of seismic events.
Boundaries of the areal source zones were developed based on regional geology, tectonic
regime, and similar patterns of historical seismicity. As discussed in Section 2.1, the Colorado
Plateau physiographic province extends through eastern and southern Utah through northern
Arizona. The Basin and Range province extends through western Utah, Nevada, and southern
Arizona. Within the study area, the ISB runs adjacent to the Colorado Plateau and Basin and
Range boundary (Wong and Olig, 1998 and Sbar, 1984). The boundary presented in Figure 4,
is based on observed seismicity and the delineation provided by Sbar (1984). Catalog seismicity
within each source zone was used to estimate the Gutenberg-Richter a and b parameters.
Earthquake locations within each zone are assumed to be uniformly located within the space.
Parameters for defining seismicity within each source zone include the following: minimum and
maximum depth, activity rate (number of events per year > Mmin) and b-value estimated from
the historical seismicity catalog for that zone, probability of activity, and parameters for rupture
length estimation based on magnitude.
4.2.1 Colorado Plateau
The site is located within the CP, as shown on Figure 4. This zone exhibits relatively sparse
concentrations of earthquake events. Within a 200-mile (322-km) radius, 134 events were
included in the catalog between 1910 and February 2015 within the CP source zone. One event
was of Mw ≥ 5.5. The largest earthquake event within the CP source zone developed for this
project was a Mw 5.5 event that occurred on August 18, 1912 approximately 131 miles (188 km)
from the site. Based on the historical seismicity, the closest event was an Mw 3.7 event that
occurred on June 6, 2008 approximately 12 miles (19 km) from the site.
As discussed previously, the a- and b-values for the Gutenberg-Richter recurrence relationship
were estimated using the maximum likelihood method developed by Weichert (1980) and the
collected seismicity for the project-specific CP source zone. The estimated b-value for the CP is
0.88 and the calculated activity rate is 0.07 earthquake events per year greater than Mw 5.0. The
cumulative event rates with magnitude for the CP are shown in Figure 5, along with the 5
percent and 95 percent confidence intervals at each magnitude increment. Figure 5 only shows
the fit to the data and the development of the a and b parameters; the figure does not show a
representation of the truncated exponential recurrence relationship used in the PSHA. A
maximum magnitude of Mw 6.75 was used for the CP, based on Wong and Olig (1998). A
maximum magnitude of 6.0 to 6.5 is recommended in the study area and a standard error of ±
0.25 was added for an upper estimate of Mw of 6.75. The maximum magnitude value is also
equivalent to the Intermountain Seismic Belt’s maximum magnitude. The minimum and
maximum depth of events specified for the CP is 1.9 miles and 12 miles (3 km and 20 km),
respectively. The CP background source has a maximum magnitude of 6.75 and magnitudes
below 7.0 are not likely to rupture the surface, therefore the minimum depth was assigned to be
1.9 miles (3 km).
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4.2.2 Intermountain Seismic Belt
Within the study area, the ISB exhibited a denser distribution of historical earthquake events
than the CP. Within the ISB source zone, 200 events were included in the catalog between
1887 to February 2015. Four events were Mw 5.5 or greater. Of the events within the study area,
the largest earthquake event within the ISB was an Mw 6.5 that occurred on November 14, 1901
approximately 164 miles (264 km) from the site.
The estimated b-value for the ISB is 0.84 and the calculated activity rate is 0.15 earthquake
events per year greater than Mw 5.0. The cumulative event rates with magnitude for the ISB are
shown in Figure 6, along with the 5 percent and 95 percent confidence intervals at each
magnitude increment. Figure 6 only shows the fit to the data and the development of the a and b
parameters; the figure does not show a representation of the truncated exponential recurrence
relationship used in the PSHA. A maximum magnitude of Mw 6.75 was used for the ISB based
on the recommendation of dePolo (1994) of an Mmax 6¾. Mw 6.75 is a generally-accepted
maximum magnitude within the Basin and Range Province. The minimum and maximum depth
of events specified for the ISB is 1.9 miles and 12 miles (3 km and 20 km), respectively. The
ISB areal zone has a maximum magnitude of 6.75 and magnitudes below 7.0 are not likely to
rupture the surface, therefore the minimum depth was assigned to be 1.9 miles (3 km).
4.3 Shear Wave Velocity
The following paragraphs summarize the method used to calculate a site-specific shear wave
velocity for use in the PSHA. The time-averaged shear-wave velocity in the top 30 meters at
the site (Vs30) was calculated from measured seismic refraction data. The uncertainty in the Vs30
estimation was addressed in the PSHA by calculating a lower bound, best estimate, and upper
bound Vs30, as described below.
4.3.1 Summary of Site-Specific Vp Values
As discussed in Section 2.2, the site is underlain by the Dakota Sandstone, predominately
composed of cross-bedded, fine-to coarse-grained, well-cemented sand (Denison, 2011).
Borings were drilled across the site by Dames & Moore in 1977 to depths ranging from 6.5 to
132.4 feet (Dames & Moore, 1978). The boring locations are shown on Figure 7, and the boring
logs are provided in Attachment 4. The boring logs show sandstone underlying the site to
depths greater than 132 feet.
Site-specific compression wave velocity (Vp) data are available for the White Mesa site from
Nielsons Incorporated (1978). During site characterization for construction of the tailings cells,
Nielsons performed thirteen seismic refraction surveys at several locations across the site to
estimate the compressive wave velocity and depth to bedrock, and to evaluate the excavation
characteristics of the material underlying the proposed cells. Nielsons reported Vp values for
various soils and rock to a depth of 33 feet. Locations of the seismic refraction surveys and
measured Vp data are shown in Figure 7.
Seismic refraction survey results show unconsolidated and/or compact soil to depths ranging
from 4 to 18 feet, overlying Dakota Sandstone. This upper soil material was excavated during
grading and construction of the tailings cells, as documented in the design and construction
completion reports (D’Appolonia, 1979, 1981, 1982; Energy Fuels Nuclear, 1983; Geosyntec,
2006, 2007) and by personal communication with site personnel (Roberts, personal
communication, 2013). Sheet 7 and Sheet 8 of D’Appolonia (1979) are cross sections through
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the tailings cells showing the planned excavation of the tailings cells below through the upper
soil material and into shallow bedrock.
The Nielsons report divides the Dakota Sandstone into four categories based upon compressive
wave velocity, as summarized below (with the reported range of measured Vp values):
Soft Rippable Rock (Vp = 3,100 to 4,000 ft/s)
Medium Soft Rippable Rock (Vp = 3,500 to 4,500 ft/s)
Medium Hard Rippable Rock (Vp = 5,000 ft/s)
Drill & Shoot Rock (Vp = 6,500 to 8,400 ft/s)
At all of the seismic survey locations, Vp increased with depth. At seven out of the thirteen
locations, “Drill & Shoot Rock” was encountered as the deepest material (Vp = 6,500 to 8,400
ft/s). The Vp value was less than 4,000 ft/s at the greatest depths profiled at only two of the
survey locations.
As shown on Figure 7, two of the seismic refraction surveys (S-12 and S-13) were conducted
more than 2,000 feet north of the existing mill and impoundment area and are not considered
relevant to the tailings impoundment reclamation design. The remaining eleven seismic
locations (S-1 through S-11) are relevant to the current study because they are within or near
the footprint of the existing tailings cells, or they are in areas of potential future tailings facility
expansion. For these eleven locations, the Vp values for the Dakota Sandstone ranged from
3,100 ft/s to 8,400 ft/s at the greatest depth profiled, with an average value of 6,009 ft/s and a
median value of 6,500 ft/s.
Based on these site-specific Vp values, a Vp of 6,500 ft/s was chosen as the best estimate of the
compression wave velocity for the upper 100 feet (30 meters) of material underlying the site.
This value is the median value of compressive wave velocities measured at a depth of 33 feet
(10 meters) (the greatest depth profiled at each relevant location) underlying or near the cells.
Compressive wave velocities at depths greater than 33 feet (10 meters) are expected to be
equal to or greater than the velocity at 33 feet (10 meters), since measured Vp increases with
depth at each survey location. Thus, the velocity measured at the bottom of the profile at a
depth of 33 feet (10 meters) is considered potentially conservative, but is the most
representative measurement of Vp for the entire upper 30 meters (100 feet) of material at the
site.
To account for uncertainty in the Vp data measured across the site, a lower bound and upper
bound Vp was estimated from the site data. Vp values of 4,400 ft/s to 7,400 ft/s envelope the
compression wave velocity for the site. This range of values encompasses all but three of the
Vp data measured at the site at the deepest depth profiled, and is approximately equivalent to
plus or minus one standard deviation from the average. The three values not included are the
two lowest values (3,100 ft/s and 4,000 ft/s) measured more than 300 ft from the tailings cells,
and the highest value measured at the site (8,400 ft/s).
4.3.2 Development of Vp/Vs Ratio
To estimate the shear wave velocity (Vs) from the compression wave velocity (Vp) measured at
the site, it is necessary to assume a Vp/Vs ratio. A Vp/Vs ratio can be calculated from a
Poisson’s ratio, or an appropriate Vp/Vs ratio can be found in the literature. Several published
references were reviewed to determine typical Poisson’s ratios for sandstone. We also
reviewed several references to determine the typical range of the Vp/Vs ratio and the typical
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range of Vs for sandstone. These references were reviewed to select the most appropriate
Vp/Vs ratio, and verify that the computed values for VS30 fall within the expected range for the
material.
Poisson’s ratios from select references are summarized below:
Goodman (1989) provides a table of Poisson’s ratios for various rock specimens, as
determined from laboratory unconfined compression testing. The following Poisson’s
ratio values are presented for three sandstone samples: 0.38 (Mississipian Berea
Sandstone from Ohio), 0.46 (Jurassic Navajo Sandstone from Arizona), and 0.11
(Pennsylvian Tensleep Sandstone from Wyoming).
Burger (1992) presents a table of laboratory-measured elastic properties for common
rocks. A Poisson’s ratio of 0.06 is presented for a sandstone sample from Wyoming.
Hatcher (1990) presents a table of Poisson’s ratios for various rock types. A value of
0.26 is presented for Mississippian sandstone from Berea, Ohio.
Unpublished notes by Dr. David Boore of the USGS (Boore, 2007) were
reviewed. These notes present an evaluation of Poisson’s ratio calculated from Vp and
Vs data from over 300 boreholes in California which were logged using surface source,
downhole receiver method or P-S suspension logging. The notes indicate a range of
Poisson’s ratio from about 0.2 to 0.48 for the various materials, including unconsolidated
sediments, with the data centered around a Poisson’s ratio of about 0.3. Dr. Boore
concludes that the Poisson’s ratio is generally less than 0.4 for materials above the
water table.
Several studies were also reviewed to determine typical Vp/Vs ratios for sandstone, and to
determine the typical range of Vs values for sandstone:
Castagna et al. (1985) present a variety of data related to the relationship between Vs
and Vp for clastic silicate rocks. For dry sandstones, the paper reports that both
laboratory data and modeling results indicate a nearly constant Vp/Vs ratio of 1.4 to 1.5.
The reported Vs values for dry sandstone range from approximately 500 to 3,500 m/s,
with most values in the range of approximately 1,500 to 3,500 m/s.
Wu and Liner (2011) present a case study that compares shear wave and compression
wave velocities for the Dickman field in Ness County, Kansas. For sandstones, the
paper reports Vp/Vs ratios ranging from 1.6 to 2.0. The paper presents estimated Vs
values that range from approximately 1,000 to 2,300 m/s for depths less than 500 m.
Lin and Heuze (1986) reviewed sonic borehole logs for boreholes drilled in Colorado and
Wyoming through shales and sandstones of the Mesaverde formation. The authors
computed in-situ Vp and Vs values from the sonic data, and a review of these results
indicates Vp/Vs ratios ranging from 1.5 to 1.8 for both shales and sandstones. The
associated Vs values (measured in-situ) range from approximately 1,800 to 2,800 m/s for
all depths evaluated in the study.
Han et al. (1986) present Vp and Vs values measured on 75 laboratory samples of
sandstone. The samples had a variety of clay content values and were measured at
confining pressures ranging from 5 to 40 MPa. Nearly all of the computed Vp/Vs ratios
fall within the range of 1.5 to 2.0. The reported laboratory-measured Vs values range
from approximately 1,500 to 3,600 m/s.
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Willis and Clahan (2006) present mean Vs30 values for a variety of California geological
units. Vs was measured at 24 sites underlain by Tertiary bedrock, and the paper
presents a mean Vs30 value of 515 m/s for Tertiary sandstone. Vs was measured at
6 sites underlain by Cretaceous sandstone, and the paper presents a mean Vs30 of
566 m/s for this material.
The references regarding Poisson’s ratio indicate that the ratio for sandstone, in particular the
laboratory-measured ratio, can have a broad range, from as low as 0.06 to as high as 0.46. Of
particular interest is the range of values presented in Boore (2007) (about 0.2 to 0.48) because
this range of values was derived from in-situ downhole data.
The studies regarding the Vp/Vs ratio indicate that typical ratios for sandstones generally range
from about 1.4 to 2.0. The Vs values presented in the studies indicate Vs values ranging from
about 500 to 3,600 m/s, with most values greater than 1,000 m/s.
Based on this review, a Poisson’s ratio of 0.35 was selected to compute a best estimate Vp/Vs
ratio. The Poisson’s ratio of 0.35 falls within the range of laboratory-measured data presented
by Goodman (1989), Burger (1992) and Hatcher (1990), and is near the center of the in-situ
data presented by Boore (2007). Using a Poisson’s ratio of 0.35, a Vp/Vs ratio of 2.1 was
computed. This value is slightly higher than the range of values discussed above, and is
therefore considered potentially conservative.
To account for epistemic uncertainty in the Vp/Vs ratio, a range of values of 1.9 to 2.3 was
evaluated. This range of Vp/Vs ratios is representative of a Poisson’s ratio ranging from 0.31 to
0.38.
4.3.3 Estimation of Site-Specific Vs Values
Site-specific Vs30 values were computed from the upper bound, lower bound, and best estimate
Vp values using the Vp/Vs ratios described in Section 4.3.2. The results envelope the Vs30 data
as follows:
A lower bound Vs30 calculated from the lower bound Vp of 4,400 ft/s (1,340 m/s) and a
Vp/Vs ratio of 2.3.
A best estimate Vs30 calculated from the best estimate Vp of 6,500 ft/s (1,980 m/s) and a
Vp/Vs ratio 2.1.
An upper bound Vs30 calculated from the upper bound Vp of 7,400 ft/s (2,255 m/s) and a
Vp/Vs ratio of 1.9.
The resulting Vs30 values range from 583 m/s to 1,187 m/s, as shown in Table 5. For purposes
of the PSHA, Vs30 values of 580 m/s, 940 m/s, and 1,190 m/s were evaluated in the PSHA to
envelope the PGA. These values were compared to the Vs values published in the references
discussed above. The values used in the analysis fall within the low end of the expected range
of values for sandstone (500 to 3,600 m/s).
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Table 5. Envelope of Vp and Vs Values for the White Mesa Site
Measured
Vp
Computed
Vs
Vs Used in
Analysis
(ft/s) (m/s) (m/s) (m/s)
Lower Bound 4,400 1,340 583 580
Best Estimate 6,500 1,980 943 940
Upper Bound 7,400 2,255 1,187 1,190
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5.0 GROUND MOTION PREDICTION EQUATIONS
GMPEs are applied to earthquakes to estimate the ground motion at the site. GMPEs are
mathematical expressions that define how seismic waves propagate from the source to the site.
Several factors combine to cause the decrease in amplitude or intensity as the wave travels to
the site, including refraction, reflection, diffraction, geometric spreading, and absorption.
GMPEs estimate the ground motion as a function of magnitude, distance, and site conditions
(e.g. soil, rock, or Vs30). The relationships are derived by fitting equations to data obtained by
strong-motion instruments for a specific region.
For the crustal faults, the following Next Generation of Attenuation (NGA) relationships were
used: Abrahamson, et al. (2014), Boore, et al. (2014), Campbell and Bozorgnia (2014), and
Chiou and Youngs (2014). Idriss (2014) was not used because the maximum applicable
distance is limited to 93 miles (150 km) and the areal source zones extend to a 200-mile (322-
km) radius.
Current NGA West 2 relationships were used as the GMPEs for the crustal faults and the areal
source zones. The GMPEs were equally weighted. It should be noted that the GMPEs
implemented in this study use the best available information, as these models have been shown
to be applicable worldwide. Table 6 lists the relationships and the associated weights. The
logarithmic mean of the four NGA relationships was used.
Table 6. GMPEs used in the PSHA
GMPE Weight
Abrahamson, et al. (2014) 0.25
Boore, et al. (2014) 0.25
Campbell and Bozorgnia (2014) 0.25
Chiou and Youngs (2014) 0.25
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6.0 PROBABILISTIC SEISMIC HAZARD ANALYSIS
The following sections describe the PSHA methodology, inputs for analysis, and results.
6.1 PSHA Code and Methodology
The methodology for PSHA was developed by Cornell (1968), and is used to provide a
framework in which uncertainties in size, location, and rate of recurrence of earthquakes can be
considered to provide a probabilistic understanding of seismic hazard.
A PSHA can be described as a procedure of four steps (Kramer 1996):
Identification and characterization of earthquake sources, along with the assignment of a
probability distribution to each source zone
Characterization of earthquake recurrence
Estimation of ground motion produced at the site by earthquakes of any possible size
occurring at any possible point in each source zone
Calculation of the probability that the ground motion parameter will be exceeded during a
particular time period given uncertainties in earthquake location, earthquake size and
ground motion parameters
Calculations for this report were performed using the computer code HAZ43, developed by Dr.
Norman Abrahamson. Earlier versions of this code were verified under the PEER PSHA Code
Verification Workshop (Thomas et al., 2010).
6.2 PSHA Inputs
A PSHA uses a combination of areal sources and fault sources. Exponential relationships were
developed to characterize the seismicity of the areal source zones. Historical seismicity was
used to characterize activity based on Gutenberg-Richter relationships within each of the
seismic zones that are shown in Figure 4. Areal sources are described in Section 4.2 and the
GMPEs considered are explained in Section 5.0.
Additional input parameters [depth to (1.0 km/s) (Z1.0) and depth to (2.5 km/s) (Z2.5)] were
estimated from the input Vs30 value. Each of these values are summarized in Table 7.
Table 7. PSHA Input Parameters
Input Parameter Value
VS30 ft/s (m/s) 1,903 ft/s
(580m/s)
3,083 ft/s
(940 m/s)
3,904 ft/s
(1,190 m/s)
Z1.0 (km) 0.152 km 0.012 km 0.0 km
Z2.5 (km) 0.827 km 0.476 km 0.363 km
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6.2.1 Areal Source Zones
Characteristics of the two areal source zones (the CP and the ISB) included in this analysis are
described in Section 4.2. The earthquake recurrence for the areal source zones is based on the
rate of historical seismicity within each zone and does not include Gaussian smoothing. The
estimation of the recurrence parameters for each source zone was presented in Section 4.2.
Although recurrence parameters were developed considering events with magnitudes as low as
Mw 3.0, a minimum magnitude of Mw 5.0 was used in the probabilistic analysis, as events with
magnitudes less than Mw 5.0 are unlikely to generate a significant hazard at the site. The
maximum magnitude assigned to the areal source zones was Mw 6.75.
6.2.2 Fault Sources
Quaternary faults that meet the minimum criteria presented in Table 4 were included in the
analysis. The mapped fault lineation (USGS et al., 2013) was simplified in the analysis by
tracing the mapped lineation and redrawing the faults as they appear in Figure 8.
Fault recurrence were modeled as both characteristic and truncated exponential. Characteristic
events were assigned a probability of 0.7 and the exponential model was weighted 0.3. The
weighting was set to balance out the two different models. The truncated distribution predicts a
higher ratio of lower magnitudes to higher magnitudes than is observed on a single fault. In
contrast, the characteristic model, in its most simple application, predicts fewer earthquakes on
a fault than are generally observed. Additional information on the fault parameters, including
dip, slip rate, depth, type of fault, and probability of activity, is included in Attachment 2.
6.3 Probabilistic Seismic Hazard Analysis Results
Ground motions at the site are were calculated for the average horizontal component of motion
in terms of PGA. In order to bracket the PGA and account for uncertainty in the site-specific
Vs30, the PGA was calculated for the range of Vs30values presented in Section 4.3.3. The
results are summarized below in Table 8 and shown on Figure 9.
Table 8. PSHA Results
Return Period Vs30
(ft/s)
Vs30
(m/s)
Mean PGA
(g)
10,000
1,903 580 0.19
3,084 940 0.15
3,904 1,190 0.14
The PSHA is used to calculate the annual frequency of exceeding a specified ground motion
level. The results of the PSHA are typically presented in terms of ground motion as a function
of annual exceedance probability. Figure 10 9 shows the total hazard curve plotted for the
lower bound Vs30 of 1,903 ft/s (580 m/s) which resulted in the highest mean PGA. At the
10,000-year return period, the hazard is controlled by the background earthquake from the CP
areal source zone. The ISB and crustal faults have little effect on the total hazard due to the
distance from the site. The Uniform Hazard Spectra (UHS) was computed for the 10,000 year
return period at each of the VS30 values. The UHS is shown in Figure 10. . At the 10,000-year
return period, the hazard is controlled by the background earthquake from the CP areal source
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zone. The ISB and crustal faults have little effect on the total hazard due to the distance from
the site.
The hazard was deaggregated to evaluate the magnitude and distance contributions to the
lower bound Vs30 or highest mean PGA for each VS30 value. The deaggregation of the hazard
allows the probability density to be calculated for selected distance and magnitude bins. The
deaggregated hazard is shown on Figures 11 through 13. The plots also include mean
magnitude, mean distance, and mean epsilon values. Figures 11 through 13 all shows that the
hazard is generally dominated by earthquakes greater than Mw 5.0 located less than 19 miles
(30 km) from the site. In summary, the disaggregation results for the three shear wave velocities
are as follows:
For a VS30=1,903 ft/s (580 m/s), the mean magnitude was calculated to be 5.78 at a
mean distance of 27 km (Figure 11), and the modal magnitude was calculated to be 5.5
at modal distance of 12.4 miles (20 km).
For a VS30=3,084 ft/s (940 m/s), the mean magnitude was calculated to be 5.77 at a
mean distance of 28 km (Figure 12), and the modal magnitude was calculated to be 5.5
at modal distance of 12.4 miles (20 km).
For a VS30=3,904 ft/s (1,190 m/s), the mean magnitude was calculated to be 5.77 at a
mean distance of 28 km (Figure 13), and the modal magnitude was calculated to be 5.5
at modal distance of 12.4 miles (20 km).
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7.0 RESULTS AND COMPARISON WITH PREVIOUS STUDIES
Based on the results of this PSHA, the mean PGA for reclaimed (long-term) conditions is
estimated to range from 0.14 g to 0.19 g. This PGA is associated with an average return period
of 10,000 years, or a probability of exceedance of 2 percent to 10 percent for a design life of
200 to 1,000 years, respectively. The Vs30 values used for the analysis ranged from 1,903 ft/s to
3,904 ft/s (580 m/s to 1,190 m/s). Selection of the PGA or a pseudostatic coefficient used for
reclamation design shall be performed during final design and be based on the results
presented in Table 8. For all VS30 values, the controlling earthquake is estimated as magnitude
5.5 at a distance of 12.4 mile (20 km).
Results of this site-specific PSHA were compared to previous analyses conducted for the site
(MWH, 2012). Results of MWH, 2012 indicate a PGA of 0.15 g for a return period of 9,900
years, using an estimated Vs30 of 2,493 ft/s (760 m/s). The PGA for reclaimed conditions from
MWH (2012) is equal to the best estimate PGA value calculated in this PSHA.
Additionally, results of this site-specific PSHA were compared to USGS 2014 NSHMP gridded
hazard curves. The USGS 2014 NSHMP indicate a PGA of 0.10 g for a return period of 2,475
years, which compare well to this study’s result of 0.10 g at a VS30 of 3,904 ft/s (580 m/s) for the
same return period. For a return period of 10,000 years, using an estimated Vs30 of 2,493 ft/s
(760 m/s), the 2014 NSHMP PGA is about 0.23 g, which is approximately 0.04 g greater than
the highest PGA calculated in this PSHA. The USGS NSHMP methodology was developed for
return periods up to 2,475 years, meaning that estimating the 10,000-year return period from the
2014 NSHMP is outside the intended use of the data and likely explain the differences in the
PGA.
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8.0 REFERENCES
Abrahamson, N.A., W.J. Silva, and R. Kamai (2014) Summary of the ASK14 Ground-Motion
Relation for Active Crustal Regions. Earthquake Spectra. Volume 30, Issue3. August.
Ake, J., K. Mahrer, D. O’Connell, and L. Block, 2005. Deep-injection and Closely Monitored
Induced Seismicity at Paradox Valley, Colorado: Bulletin of the Seismological Society of
America, v. 95, p. 664-683.
Arabasz, W.J., S.J. Nava, M.K. McCarter, K.L. Pankow, J.C. Pechmann, J. Ake, and A. McGarr,
2005. Coal-Mining Seismicity and Ground-Shaking Hazard: A Case Study in the Trail
Mountain Area, Emery County, Utah. Bulletin of the Seismological Society of America, v.
95, pp. 18-30.
Boore, P.M., J.P. Stewart, E. Seyhan, and G.M. Atkinson (2014). NGA-West 2 Equations for
Predicting PGA, PGV, and 5%-Damped PSA for Shallow Crustal Earthquakes.
Earthquake Spectra. Volume 30, Issue 3. August.
Boore, D. M., 2007. Dave Boore’s notes on Poisson’s ratio (the relation between Vp and
Vs. Unpublished notes available at www.daveboore.com. March 24.
Campbell, K. W., and Y. Bozorgnia, (2014). NGA-West2 Ground Motion Model for the Average
Horizontal Components of PGA, PGV, and 5%-Damped Linear Acceleration Response
Spectra. Earthquake Spectra. Volume 30, Issue 3. August
Castagna, J.P., M.L. Batzle and R.L. Eastwood. 1985. Relationships between compressional-
wave and shear-wave velocities in clastic silicate rocks. Geophysics, Vol. 50, No. 4, pp.
571-581.
Chiou, B. S., and R.R. Youngs, 2014. Update of the Chiou and Youngs NGA Model for the
Average Horizontal Component of Peak Ground Motion and Response Spectra.
Earthquake Spectra. Volume 30, Issue 3. August.
Colorado Geological Survey (CGS), Undated. Earthquakes Triggered by Humans in Colorado –
A Background Paper.
Cornell, C.A. 1968. Engineering seismic risk analysis, Bulletin of Seismological Society of
America, v.58 p. 1583-1606.
Dames & Moore, 1978. Environmental Report, White Mesa Uranium Project, San Juan County,
Utah, for Energy Fuels Nuclear, Inc. January 30.
D’Appolonia. 1979. Engineers Report, Tailings Management System, White Mesa Uranium
Project, Blanding, Utah. June.
D’Appolonia. 1981. Engineer’s Report, Second Phase Design – Cell 3, Tailings Management
System, White Mesa Uranium Project, Blanding, Utah. May.
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23 March April 2015
D’Appolonia. 1982. Construction Report, Initial Phase – Tailings Management System, White
Mesa Uranium Project. Prepared for Energy Fuels Nuclear, Inc. February.
Denison Mines (USA) Corporation. (Denison) 2011. Reclamation Plan, White Mesa Mill,
Blanding Utah, Radioactive Materials License No. UT1900479, Rev. 5. September.
dePolo, C.M., 1994. The Maximum Background Earthquake for the Basin and Range Province,
Western North America. Bulletin of the Seismological Society of America, v. 84, no. 2, p.
446-472. April.
Energy Fuels Nuclear, Inc., 1983. Construction Report, Second Phase, Tailings Management
System. March.
Energy Fuels Resources (USA) Inc. (EFRI), 2012. Responses to Interrogatories – Round 1 for
Reclamation Plan, Revision 5.0, March 2012. August 15.
Geosyntec Consultants, 2006. Cell 42A Lining System Design Report for the White Mesa Mill,
Blanding, Utah. January.
Geosyntec Consultants, 2007. Cell 4B Design Report, White Mesa Mill, Blanding, Utah.
December.
Han, D-h, A. Nur and D. Morgan, 1986. Effects of porosity and clay content on wave velocities
in sandstones. Geophysics, Vol. 51, No. 11, pp. 2093-2107.
Hecker, S., 1993. Quaternary Tectonics of Utah with Emphasis on Earthquake-hazard
Characterization. Utah Geological Survey Bulletin 127.
Idriss I. M., 2014. An NGA Empirical Model for Estimating the Horizontal Spectral Values
Generated By Shallow Crustal Earthquakes. Earthquake Spectra. Volume 30, Issue 3.
August.
Kramer, S.L., 1996. Geotechnical Earthquake Engineering, Upper Saddle River, New Jersey,
Prentice Hall.
Lin, W. and F.E. Heuze, 1986. In-Situ Dynamic Elastic Moduli of Mesaverde Rocks and a
Comparison with Static and Dynamic Laboratory Moduli. Lawrence Livermore National
Laboratory (Unconventional Gas Program, Western Gas Sands Research). UCID-
20611.
MFG, Inc., 2006. White Mesa Uranium Facility, Cell 4 Seismic Study, Blanding, Utah.
November 27.
MWH, 2012. Memorandum: Site-Specific Probabilistic Seismic Hazard Analysis, White Mesa
Uranium Facility, Blanding, Utah. May 30.
Nielsons Incorporated, 1978. Seismograph Survey of Blanding Mill Site, San Juan County,
Utah. Prepared for Energy Fuels Nuclear, Inc.
Petersen, M.D., M.O. Moschetti, P.M. Powers, C.S. Mueller, K.M. Haller, A.D. Frankel, Y. Aeng,
S. Rezaeian, S.C. Harmsen, O.S. Boyd, N. Field, R. Chen, K.S. Rukstales, N. Luco, R.S.
Probabilistic Seismic Hazard Analysis
Energy Fuels Resources (USA) Inc. MWH Americas, Inc.
24 March April 2015
Wheeler, R.A. Williams, and A.H. Olsen, 2014. Documentation for the 2014 Update of
the United States National Seismic Hazard Maps. United States Geological Survey
Open-File Report 2014-1091.
Reasenberg, P., 1985. Second-order moment of central California seismicity, 1969-82, J.
Geophys. Res., 90, 5479 - 5495.
Roberts, H., 2013. Personal communication from Harold Roberts, Energy Fuels (USA) Corp., to
Melanie Davis, MWH Americas, Inc. May 29.
Swanson, P., C. Stewart, and W. Koontz, 2008. Monitoring Coal Mine Seismicity with an
Automated Wireless Digital Strong-Motion Network. In: Proceedings of the 27th
International Conference on Ground Control in Mining, July 29 - July 31, 2008,
Morgantown, West Virginia, pg. 79-86.
Tetra Tech, Inc., 2008. Seismic Hazard Analysis for Shootaring Canyon Uranium Processing
Facility. April.
Thomas, P., I. Wong, and N. Abrahamson, 2010. Verification of Probabilistic Seismic Hazard
Analysis Computer Programs. May.
Sbar, M.L. 1982. Delineation and Interpretation of Seismotectonic Domains in Western North
America. Journal of Geophysical Research, v. 87, no. B5, p. 3919-3928. May.
Stepp, J.C., 1972. Analysis of the completeness of the earthquake hazard sample in the Puget
Sound area and its effects on statistical estimates of earthquake hazard, Proc. Intern.
Conf. Microzonation for Safer Construct. Res. Appl., Seattle, Washington 2, 897-909.
URS, 2015. Review Comments on White Mesa Mill, Probabilistic Seismic Hazard Analysis
Report. January.
URS, 2015b. Review of Energy Fuels Resources (USA) Inc., White Mesa Mill, [Updated]
Tailings Data Analysis Report (March 2015) and [Updated] Probabilistic Seismic Hazard
Analysis Report (March 2015) prepared by MWH Americas, Inc. – URS Project No.
UT11.1102.004. March.
U.S. Department of Energy (DOE), 1989. Technical Approach Document: Revision II, UMTRA-
DOE/AL 050425.0002, Uranium Mill Tailings Remedial Action Project. Washington, D.C.
U.S. Geological Survey (USGS). 2013. Arizona Geological Survey, Colorado Geological Survey,
Utah Geological Survey, New Mexico Bureau of Mines and Mineral Resources, 2006.
Quaternary fault and fold database for the United States, accessed May 7, 2013, from
USGS web site: http://earthquake.usgs.gov/hazards/qfaults.
U.S. Nuclear Regulatory Commission (NRC). 2013. 10 CFR Appendix A to Part 100 – Seismic
and Geologic Siting Criteria for Nuclear Power Plants. http://www.nrc.gov/reading-
rm/doc-collections/cfr/part100/part100-appa.html. Accessed March.
U.S. Nuclear Regulatory Commission (NRC), U.S. Department of Energy (DOE), and Electric
Power Research Institute (EPRI); (CEUS-SSCn). 2012. Technical Report: Central and
Eastern United States Seismic Source Characterization for Nuclear Facilities.
Probabilistic Seismic Hazard Analysis
Energy Fuels Resources (USA) Inc. MWH Americas, Inc.
25 March April 2015
Utah Department of Environmental Quality, Division of Radiation Control (DRC). 2013. Review
of August 15, 2012 (and May 31, 2012) Energy Fuels Resources (USA), Inc. Responses
to Round 1 Interrogatories on Revision 5 Reclamation Plan Review, White Mesa Mill,
Blanding, Utah, report dated September, 2011. February 13.
Weichert, D. 1980. Estimation of the earthquake recurrence parameters for unequal observation
periods for different magnitudes. Bulletin of the Seismological Society of America 70:
1337-1346.
Wong, l.G., and J.R. Humphrey, 1989. Contemporary seismicity, faulting, and the state of stress
in the Colorado Plateau, Geological Society of America Bulletin 101: 1127-1146.
Wong, l.G., S.S. Olig, and J.D.J. Bott, 1996. Earthquake potential and seismic hazards in the
Paradox Basin, southeastern Utah, In A.C. Huffman, W.R. Lund, and L.H. Godwin, eds.,
Geology and Resources of the Paradox Basin, 1996 Special Symposium, Utah
Geological Association and Four Corners Geological Society Guidebook 25: 241-250.
Wong, I.G., S.S. Olig, B.W. Hassinger, and R.E. Blublaugh. 1997. Earthquake hazards in the
Intermountain US: Issues relevant to uranium mill tailings disposal. In Proceedings of
the Fourth International Conference of Tailings and Mine Waste ’97, Fort Collins,
Colorado, USA, January 13-17, p. 203-212.
Wong, I.G. and S.S. Olig. 1998. Seismic Hazards in the Basin and Range Province:
Perspectives from Probabilistic Analyses. In Western States Seismic Policy Council
Proceedings. p. 110-127.
Wu, Q. and C. Liner. 2011. Case study: Comparison on shear wave velocity estimation in
Dickman field, Ness County, Kansas. 2011 SEG San Antonio Annual Meeting.
Probabilistic Seismic Hazard Analysis
FIGURES
Probabilistic Seismic Hazard Analysis
ATTACHMENT 1
LIST OF EARTHQUAKE EVENTS WITHIN THE WHITE MESA STUDY AREA
Probabilistic Seismic Hazard Analysis
ATTACHMENT 2
LIST OF FAULTS AND FAULT CHARACTERISTICS INCLUDED IN THE PSHA
Probabilistic Seismic Hazard Analysis
ATTACHMENT 3
SUMMARY OF INDIVIDUAL FAULT PARAMETERS
Probabilistic Seismic Hazard Analysis
ATTACHMENT 4
DAMES & MOORE BORING LOGS (1978)