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Nuclear Engineering and Design 259 (2013) 222– 229

Contents lists available at ScienceDirect

Nuclear Engineering and Design

jo u r n al hom epage : www.elsev ier .com/ locate /nucengdes

evelopment of probabilistic seismic hazard analysis for international sites,hallenges and guidelines

ntonio Fernandez Ares ∗, Ali Fatehi1

aul C. Rizzo Associates, Inc., 500 Penn Center Boulevard, Penn Center East, Suite 100, Pittsburgh, PA 15235, USA

r t i c l e i n f o

rticle history:eceived 30 June 2010

a b s t r a c t

This article provides guidance to conduct a site-specific seismic hazard study, giving suggestions forovercoming those challenges that are inherent to the significant amounts of epistemic uncertainty for

eceived in revised form 22 October 2010ccepted 12 January 2011

sites at remote locations. The text follows the general process of a seismic hazard study, describing boththe deterministic and probabilistic approaches. Key and controversial items are identified in the areasof recorded seismicity, seismic sources, magnitude, ground motion models, and local site effects. A casehistory corresponding to a seismic hazard study in the Middle East for a Greenfield site in a remotelocation is incorporated along the development of the recommendations. Other examples of analysis

the W

case histories throughout

. Introduction

The use of building codes to establish seismic design basisarameters is applicable to regions where:

. sufficient earthquake data is available, conditions typical of thepopulated regions with recorded historical and instrumentalseismicity;

. extensive research is well documented;

. the performance criteria of the code in place are applicable andconsistent with the expected lifespan and functionality of thestructure.

. if any of the previous three conditions are not met, a site-specificseismic hazard analysis is either required or highly recom-mended. For example, a nuclear power plant (NPP) located neara major urban region with moderate to high seismicity will meetthe first and second criteria, but not necessarily the third, sincehigh profile projects are expected to perform satisfactorily underhigher seismic demand.

This article provides guidance to conduct a site-specific seismic

azard study, giving suggestions for overcoming those challengeshat are inherent to the significant amounts of epistemic uncer-ainty for sites at remote locations. The text follows the generalrocess of a seismic hazard study, describing both the determin-

∗ Corresponding author. Tel.: +1 412 200 5381.E-mail addresses: antonio.fernandez@rizzoassoc.com (A. Fernandez Ares),

li.fatehi@rizzoassoc.com (A. Fatehi).1 Tel.: +1 412 825 2120; fax: +1 412 856 9749.

029-5493/$ – see front matter © 2011 Elsevier B.V. All rights reserved.oi:10.1016/j.nucengdes.2011.01.024

orld are presented as well.© 2011 Elsevier B.V. All rights reserved.

istic and probabilistic approaches. Key and controversial items areidentified in the areas of recorded seismicity, seismic sources, mag-nitude, ground motion models, and local site effects.

2. Deterministic and probabilistic analysis

One of the following strategies or approaches may be under-taken when performing a seismic hazard analysis:

1. Deterministic approach: uses a seismotectonic model and selectsa source with a prescribed earthquake magnitude and distance toestimate the hazard at a given location. A deterministic approachmay be thought of as a “scenario-like description” of earthquakehazard (Reiter, 1990).

2. Probabilistic approach: a probabilistic seismic hazard analysis(PSHA) estimates the annual frequency of exceedance as a func-tion of a ground measure, such as peak ground acceleration(PGA), or spectral acceleration based on geologic and seismologicdata within a probabilistic framework; (e.g., McGuire, 2004).

3. Hybrid approach: a PSHA is conducted and a deaggregationanalysis is performed to understand which distances and mag-nitudes contribute most to the hazard. A source with suchmagnitude–distance pair characteristic is selected as the con-trolling event and a deterministic analysis is performed.

Fig. 1 provides a graphic representation of the deterministic and

probabilistic approaches. The deterministic analysis is simple innature and it is ideal to perform “scenario-like” analysis. It helpsthe analyst gain insight on the effects of each source indepen-dently. It also has the advantage of allowing owners and engineersto select a controlling source that best addresses the design

A. Fernandez Ares, A. Fatehi / Nuclear Engineering and Design 259 (2013) 222– 229 223

babili

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Fig. 1. Deterministic and pro

oncerns at a particular site. If the controlling source is well defined,he deterministic approach will save time by allowing engineers tovoid the research of earthquake parameters of multiple sourceshat are not relevant to a site. The analysis may be geared towardshe controlling source and its detailed characterization, and moreeduction of epistemic uncertainty may be attained. A case-historyor which the controlling event is well defined presents itself for aower plant site in the State of Missouri in the United States (Fig. 2).he plant sits in a stable continental region located approximately20 km from the New Madrid Fault Source Zone (NMFZ), wherehe largest earthquake cluster in the continental United States haseen recorded. These events took place during the 1811–1812 win-er months. The magnitudes of the 1811–1812 events ranged from

7.0 up to M8.1 (USGS, 2008).For some cases in which a dominant controlling source is iden-

ified, a deterministic analysis is prudent, such as the NMFZ (Fig. 2).therwise, a PSHA is recommended since the results will show how

arthquake hazard varies as a function of probability of exceedance,utomatically giving an indication of the performance of the sitender different demand earthquakes. In addition, hazard acrosshe frequency spectrum is better assessed without the need of

stic seismic hazard analysis.

constructing a bounding spectra resulting from the independenthazard imposed by each source. A PSHA may be far superior to adeterministic approach. This is in general a legitimate statement,but one that needs to be taken with reservation. A PSHA must betied to a comprehensive investigation of the seismic and tectonicconditions, incorporating expertise from experienced geologists,seismologists, and engineers. Failing to do so will result in unreli-able results and wasted mathematical and computer simulations.A PSHA may “disguise” the effects of important controlling featuresso special attention needs to be placed to adequately representsources and define characteristic events. Therefore, a PSHA is notrecommended if resources for thorough research and analysis arenot available.

Probabilistic methodologies have been developed specificallyfor nuclear power plant seismic hazard assessments in the cen-tral and eastern U.S. (CEUS) (EPRI, 1986). These methodologieshave been used to calculate the seismic hazard at nuclear power

plant sites throughout the CEUS (e.g., EPRI, 2008) and muchhas been learned from these assessments. U.S. Nuclear Regula-tory Commission Regulatory Guide 1.208 (USNRC, 2007) providesthe framework for assessing the Safe Shutdown Earthquake

224 A. Fernandez Ares, A. Fatehi / Nuclear Engineering and Design 259 (2013) 222– 229

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Fig. 2. New Madrid fa

SSE) ground motion levels for new power generating nuclearlants.

Regulatory Guide 1.208 (USNRC, 2007) provides general guid-nce on procedures for (1) conducting geological, geophysical,eismological, and geotechnical investigations; (2) identifyingnd characterizing seismic sources; (3) conducting a PSHA; (4)etermining seismic wave transmission (soil amplification) char-cteristics of soil and rock sites; (5) determining a site-specific,erformance based ground motion response spectra (GMRS) lead-

ng to the establishment of an SSE.PSHA methodology allows for alternative definitions of inputs to

e incorporated in the analysis. The alternative inputs are based onhe analysis of existing information related to seismic source zona-ion, earthquake recurrence relations, maximum magnitudes, andround motion models specific to the seismotectonic environmentf the site area. Brief explanations of these inputs along with theegulatory positions as described in RG 1.208 is presented below.

. PSHA, earthquake sources

It is common practice to include all sources within a 320 kmadial region and other sources that will contribute more than one

e controlling feature.

percent of the hazard. Seismic sources are characterized as the fol-lowing:

General area sources. These sources are defined based ondistinguishable patterns of seismicity or seismotctonic bound-aries. The recurrence relationships are represented by theGuttenberg–Richter parameters in the form of the truncated expo-nential distribution (TED). The probability of an earthquake ofmagnitude m occurring at the source is obtained with the TED (Eq.(1)).

P(M > m) =∫ mmax

m

e−ˇ(m−mmin)

(1 − e−ˇ(mmax−mmin))dm (1)

where m is the magnitude; mmin is the minimum magnitude ofearthquakes in source; mmax is the maximum magnitude of earth-quakes in source; P(M > m) is the probability of occurrence of anearthquake with magnitude M larger than m; is the = b ln(10); b

is the slope in the Gutenberg–Richter (G–R) magnitude–frequencyrelation.

Fault sources. These sources are directly tied to a well identi-fied rupture zone that shows direct correlation with earthquakeactivity. Fig. 2 shows the NMFZ, a prominent fault source in the

A. Fernandez Ares, A. Fatehi / Nuclear Engineering and Design 259 (2013) 222– 229 225

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Fig. 3. Alternate

entral United States. Characteristic earthquake models have beeneveloped to model the recurrence of large magnitude earthquakeslong some of the known faults. The rate of the large earth-uakes (defined from geological observations) along these faultsas shown to have been underestimated by G–R recurrence rela-

ions (Youngs and Coppersmith, 1985).Background. Accounts for seismic activity that is not explained

y area sources or faults.There is a significant amount of uncertainty in developing the

eometry and recurrence of seismic sources. In doing so, it ismportant to account for historical seismicity, tectonic setting,nd geologic studies. In many cases, historical seismicity will behe main driver for the definition of the properties of a seismicource. Development of seismic source models involves significantmounts of epistemic uncertainty. Common questions are:

What is the maximum credible earthquake in a zone?Where are the boundaries that delineate the zone?What is the slip rate and length of a fault zone?What is the distribution of seismicity within a zone?

RG 1.208 (USNRC, 2007) states that “uncertainties associatedith the identification and characterization of seismic sources

n tectonic environments in both the CEUS and the WUS shoulde evaluated.” Characterization of seismic sources is more prob-

ematic in CEUS because there is generally no clear association

c source models.

between the seismicity and the tectonic features. Therefore,alternative representation of seismic source zones should beconsidered as input to the PSHA to account for the uncer-tainty.

In response to such challenges, the Electrical Power ResearchInstitute (EPRI) performed a high level study to define seismicsources in the CEUS. The study, which involved six expert EarthScience Teams (EST) (EPRI, 1986), developed six alternative seis-mic source models for CEUS. These seismic source models havebeen used extensively in seismic hazard assessments for NPP sitesthroughout CEUS (e.g., EPRI, 2008). Recent studies have shown thatgeometry and seismicity parameters of several source zones in EPRIsource model (EPRI, 1986) need to be updated. Most importantexamples include the Charleston and New Madrid seismic zones forwhich extensive studies resulted in updated geometries and recur-rence models. This updated information has been used in recentseismic hazard assessments for new license applications for nuclearsites in CEUS.

In 2009 an updated seismic source model was developed in theArabian Peninsula for a site in the Middle East (Rizzo, 2009). Themodel was used in a PSHA along with two independent modelsto account for epistemic uncertainty (Fig. 3) (Musson et al., 2006;Aldama-Bustos et al., 2009). The development of seismic source

models is a process that requires an in-depth analysis of exist-ing extensive research in the fields of seismicity, paleoseismicity,geology, and tectonics.

2 ngineering and Design 259 (2013) 222– 229

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Campbell-Bozorgnia, 2008Boore-Atkinson, 2008Akar-Bommer, 2007

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M = 5.0

26 A. Fernandez Ares, A. Fatehi / Nuclear E

. Earthquake catalog and recurrence

Recurrence relations that predict annual rate of earthquakes ofifferent magnitudes within a source zone, are derived from anarthquake catalog. The catalog is a list of recorded earthquakeshat provides the following information: origin time, location,epth, and some measure of earthquake size, such as magnitude.ith the earthquake catalog, it is possible to obtain the logarithmic

lopes and intercept of the recurrence model, which is conceptuallyhown in Fig. 1.

The maximum likelihood method is the most common tech-ique of deriving the earthquake recurrence parameters. Catalogsust be developed with a compilation of historical accounts of seis-icity and global and local earthquake records. Reliable catalog

ata may be obtained from organizations such as the Interna-ional Seismological Center (ISC), UK or the US Geological Surveyreliminary Determination of Epicenters (PDE). Earthquake cata-ogs need to be carefully compiled taking into account consistencyf magnitude units, de-clustering of aftershocks and foreshocks,nd completeness for periods of historical seismicity for whichnly large earthquakes are recorded. Once the seismic sources areefined and the earthquake catalog is built, it is possible to obtainhe three key and critical parameters of an earthquake source: (1)ctivity rate at zero (‘a’ value) or low magnitudes (N(m0)), (2) ‘b’alue, and (3) maximum magnitude. Careful attention needs to belaced in the way in which seismicity is distributed throughout theeismic source zone. It is important to account for the significantevels of aleatory uncertainty related to the location of future earth-uakes. A common approach in areas of low seismicity is to keephe ‘b’ value constant throughout the zone, while smoothing the ‘a’alue to each grid cell (USGS, 2008). The EPRI methodology (EPRI,986) for CEUS performs the smoothing of both ‘a’ and ‘b’ valueshroughout the seismic source zone.

The selection of maximum magnitude (Mmax) has significantmpact in the outcome of the PSHA. In some cases the recurrencenterval of maximum credible earthquake (MCE) are longer thanhe time period of recorded seismicity in the seismic zone. In suchases, the estimation of Mmax should not be based only on recordedeismicity. Again, one needs to consider credible alternative valuesased on different data, methodologies, and interpretations.

The selection of the minimum magnitude also has a significantmpact. The minimum magnitude can bias the hazard for higheresponse spectra frequencies. This bias results from incorporatinglose-in small magnitude earthquakes, whose recurrence rate isxcessive relative to larger magnitude earthquakes of engineeringignificance due to the exponential recurrence relationship. It isommon practice to adopt a value of mb 5.0, since it is well docu-ented that earthquakes with lower magnitudes have a very low

robability to cause damage to engineered facilities (USNRC, 2007).There have been several cases in which ground motions from

mall nearby earthquakes have exceeded the operating basis earth-uake (OBE) and SSE response spectra of nuclear power plants

n eastern United States (EPRI, 2007). These small events haveot caused any damage to the structures and components. Sub-equent studies led to development of the cumulative absoluteelocity (CAV) parameter that was judged to be the best engi-eering parameter for predicting the threshold of damage to thengineered structures (EPRI, 2006). Incorporating this parameter inSHA can remove the contribution of non-damaging small eventsnd therefore the associated bias form the hazard results.

. Ground motion models, PSHA computation

As previously stated, a PSHA determines the frequency for which hazard parameter such as acceleration or intensity exceeds some

Fig. 4. Comparison between the ground motion models of Campbell and Bozorgnia(2008), Boore and Atkinson (2008) and Akkar and Bommer (2007). Plots show peakground acceleration vs distance for earthquakes with magnitudes 5 and 7.

given threshold during some time period in the future. The analysisincorporates all sources in the seismotectonic model assuming thatthey can act independently; recurrence rates of earthquake eventsassociated with distance and probability distributions of maximummagnitude are included to quantify the contribution to the hazardfrom each of the seismic sources. The PSHA is conducted in the stepsindicated in Fig. 1. The integration of seismic hazard for a particularlocation is given by Eq. (2).

�(z) =∑

i

vi(m0)

∫ ∫P[Z > z|m, r]fMi(m)fRi(r) dm dr (2)

Z is the peak ground acceleration or spectral acceleration at pre-scribed natural frequencies; �(z) is the frequency with which ‘z’is exceeded; vi(m0) is the number of earthquakes per year abovea prescribed minimum magnitude (m0) in the ith seismic source;P[Z > z|m,r]f(m) is the conditional probability that Z will exceed avalue z, given the earthquake magnitude m, and distance r. f(m) andf(r) are the probability density function for magnitude and distance.

Step 3 in Fig. 1 relates to the ground motion prediction equation(GMPE). A GMPE is an attenuation model that relates the energyreleased at the earthquake location to the energy experienced at thereceiver location. In the context of the PSHA integration equation(Eq. (2)), the GMPE are represented by the conditional probabilityfactor that defines the probability of exceeding a ground motionlevel threshold, such as peak ground acceleration (PGA), conditionalto the occurrence of an earthquake at some distance away fromthe site: P(Z > z|m,r). Overall GMPEs are classified into one of thefollowing categories:

Empirical. Models primarily based on the regression analysisof earthquake strong-motion data that consists primarily of peakground or spectral acceleration, magnitude, distance, properties ofthe recording site.

Stochastic. Models that are primarily based on the stochasticsimulation of high frequency ground motions and seismologicalmodels of earthquake spectra. Stochastic models may be applied inregions for which sufficient earthquake strong-motion data are notavailable.

Analytical. Models that are developed based on numerical sim-ulations of seismic wave propagation.

Models built with a combination of the previous categories are

denominated Hybrid Models. A comparison of the form of severalground motion models used for a PSHA in a remote region is pro-vided in Fig. 4. Naturally, two questions come to mind: (1) whatattenuation model is the best fit for a particular problem; (2) howreliable is the fit provided by the attenuation model? The answer

ngineering and Design 259 (2013) 222– 229 227

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A. Fernandez Ares, A. Fatehi / Nuclear E

o both questions is not trivial since there are significant amountsf uncertainty in the answers to both questions. Epistemic uncer-ainty is associated to the first question while aleatory uncertaintys associated with the second.

Aleatory uncertainty in the use of GMPEs originates from thecatter in peak ground or spectral acceleration data at each mag-itude and distance point. The uncertainty, which is quantified inhe curve fitting process, is schematically indicated by the normalistribution in Step 3 in Fig. 1 (P(Acc > a|m)).

To account for epistemic uncertainty for a PSHA for a site projectn the Middle East, three sets of GMM were selected based onhe tectonic environments. The seismic source models shown inig. 2 indicate that ground motion originates from three types ofechanisms and/or environments: (1) active zones in the Zagros

elt, (2) the Makran subduction zone, and (3) the stable regionn the Arabian Peninsula. For this PSHA the soil properties at theite location are not consistent with the regions from which dataas reduced to develop the attenuation equations. This condition

s common at locations in which marginal or null developmentas occurred so there is no soil site-specific data and there haseen no particular interest to develop GMPEs. Careful analysis muste dedicated to gain reasonable compatibility between groundotion models and site-specific soil properties. It was therefore

equired to apply equations developed in other regions with simi-ar geologic and tectonic environments. This problem is commonlyenominated as the “target–host” consistency problem. The pre-ailing site-specific conditions considered for the development ofhe attenuation equations are referred to as the “host.” The site-pecific conditions at the location of interest are the “target.”

Proper treatment of ground-motion variability is crucial in PSHAtudies. In a review article, Bommer and Abrahamson (2006) notehat PSHA studies in recent years have resulted in higher designround-motions than had been obtained in previous assessmentserformed in the 1970s and 1980s. One of the main reasons is theact that earlier studies have either neglected the ground motionariability or have artificially reduced its influence on the hazardstimates. A known example of this is the results of recent PSHAtudies for Swiss nuclear power plant sites that show considerablencrease in hazard results compared to previous studies performedn 1980s (Bommer and Abrahamson, 2006).

The steps involved in the development of the PSHA have beenouched upon throughout the text. The outcome of the PSHA is

hazard curve, which provides ground motion levels for differ-nt annual probabilities of exceedance. Fig. 5 gives an example ofazard curves obtained for a site in the Central United States foreak Ground Acceleration (PGA) for hard rock conditions. Equiva-ent curves are developed for spectral accelerations and a uniformazard response spectra (UHRS) at hard rock conditions is builtFig. 6). This spectra represents the ground motion that is appliedo a soil column to analyze local amplification effects.

. Site amplification analysis

The final step to assess earthquake hazard is site amplification.t is well documented that, as vertically propagated shear wavesravel from the ground to the surface, the ground motion changesignificantly, especially if major contrasts in shear wave velocityre present between layers of the soil model. The goal of the ampli-cation analysis is to develop the ground motion response spectraGMRS) (USNRC, 2007). Other points of application of ground

otion may also be required and these are denominated founda-ion input response spectra (FIRS), as shown in Fig. 7, a conceptuallot showing the position of the GMRS and FIRS.

The subsurface conditions must be defined in detail since thehear wave velocity of the soil column is a key input to the

Fig. 5. Hazard curves.

amplification analysis. Therefore, a detailed geotechnical and geo-physical exploration program is required. Fig. 8 provides guidanceto develop GMRS by considering the following steps:

1. PSHA – obtain uniform hazard response spectra (UHRS);2. deaggregation – controlling events and time histories;3. site amplification analysisv – use shear wave velocity profile and

Fig. 6. Mean and median uniform hazard response spectra for 1E-4 and 1E-5 annualprobabilities of exceedance.

228 A. Fernandez Ares, A. Fatehi / Nuclear Engineering and Design 259 (2013) 222– 229

Fig. 7. GMRS and FIRS.

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the design of the Kashiwazaki-Kariwa nuclear power plant. How-ever, there was no significant visible damage to the safety relatedstructures, systems, and components. This was probably due to theconservatism introduced at different stages of design process. Thecombined effects of these conservatisms were apparently sufficient

Fig. 8. Steps involved i

. performance – apply factors to soil spectra to account for siteperformance under different probabilities;

. V/H ratio – develop vertical to horizontal ground motion ratiosand obtain the GMRS or FIRS.

An example of GMRS is shown for a site in the Central Unitedtates and is provided in Fig. 9.

. Senior Seismic Hazard Analysis Committee (SSHAC)

For a comprehensive PSHA, it is fundamental to incorporatehe expertise of the scientific community. A PSHA analyst willncounter controversy in the selection of inputs and the develop-ent of calculations. Therefore, it is recommended to incorporate

he opinion of the informed scientific community, which is rep-esented by experts in the fields of geology, seismology, andngineering (Budnitz et al., 1997). Differences in opinion betweenxperts are the rule rather than the exception, and therefore, it isot trivial to reach consensus on the selection of input and calcu-

ation approach. One of the strengths of the PSHA is that it has theechanisms in place to handle uncertainty and incorporate differ-

nt interpretations of the data into the analysis. The SSHAC should

romote the incorporation of differences of legitimate scientificpinion that exist in a seismic hazard study. Consensus should beeached on how to account for different views and interpretations.

One example is worth noting here. Ground motions from the007 Niigata Chuetsu-Oki Japan earthquake (Mw = 6.6), signifi-

evelopment of GMRS.

cantly exceeded the level of seismic input taken into account in

Fig. 9. GMRS for site in Central United States.

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mologist with Paul C. Rizzo Associates, Inc. He obtainedhis Ph.D. in geophysics from Saint Louis University. Hisresearch focused on scaling of earthquake ground motionsin Pacific Northwest and Northern California. He has beeninvolved in several seismic hazard studies for nuclear andnon-nuclear sites.

A. Fernandez Ares, A. Fatehi / Nuclear E

o compensate for uncertainties in the data and methods availablet the time of the design of the plant, which led to underestimationf the original seismic input (IAEA, 2007). This example explainshy “SSHAC” type seismic hazard studies should be performed forPP sites.

Recent PSHA studies have been performed in different SSHACevels in the CEUS and elsewhere. A comprehensive seismic hazardnalysis was performed for nuclear power plant sites in Switzerlandollowing the SSHAC level 4 procedures for expert elicitationAmrahamson et al., 2002). The study involved multiple expertsn seismic source models, ground-motion attenuation, and siteesponse analysis. A SSHAC level 4 PSHA was performed for a poten-ial nuclear waste repository site in Yucca Mountain, Nevada (Steppt al., 2001). Several expert teams were involved in the study, whichimed at estimating both the ground motion and fault displace-ent hazards at the site. The major focus of the study (believed to

e the most comprehensive at the time) was the quantification ofpistemic uncertainties in seismic source and fault displacementnputs and aleatory uncertainties in ground motion estimation.

. Conclusions

The development of a successful PSHA is a challenge thatnvolves expertise from multiple disciplines in earth science andngineering. It also requires in-depth, site-specific investigationshat include understanding the regional and site geology, seis-

icity, state-of-the-art ground motion estimation methods, andeophysical conditions. Venturing into a PSHA without a seri-us and comprehensive site-specific investigation is a futile andeaningless exercise. It is imperative to reduce uncertainty with

nvestigations that are meaningful, relevant, and implementable.ore importantly, it is essential to understand the nature of uncer-

ainty and what it means in the context of the outcome to the PSHA. PSHA must always be updated as new data and new researchecomes available. The most evident example is the occurrence ofn earthquake of unexpected magnitude or unexpected location.

eferences

brahamson, N.A., Birkhauser, P., Koller, M., Mayer-Rosa, D., Smith, P., Sprecher, C.,Tinic, S., Graf, R., 2002. PEGASOS-a comprehensive probabilistic seismic haz-ard assessment for nuclear power plants in Switzerland. In: Proceedings of theTwelfth European Conference on Earthquake Engineering , London (Paper no.633).

kkar, S., Bommer, J., 2007. Prediction of elastic displacement response spectra inEurope and the Middle East. Earthquake Engineering and Structural Dynamic36, 1275–1301.

ldama-Bustos, G., Bommer, J.J., Fenton, C.H., Stafford, P.J., 2009. Probabilistic seis-mic hazard analysis for rock sites in the Cities of Abu Dhabi, Dubai and Ra’s AlKhaymah, United Arab Emirates. Georisk 3 (2), 1–29.

ommer, J., Abrahamson, N.A., 2006. Why do modern probabilistic seismic-hazardanalyses often lead to increased hazard estimates? Bulletin of SeismologicalSociety of America 96 (6), 1967–1977.

oore, D.M., Atkinson, G.M., 2008. Ground-Motion Prediction Equations forthe Average Horizontal Component of PGA, PGV, and 5%-Damped PSA atSpectral Periods between 0.01 s and 10.0 s,. Earthquake Spectra 24 (1),99–138.

udnitz, R.J., Aostolakis, G., Boore, D.M., Cluff, L.S., Coppersmith, K.J., Cornell, C.A.,Morris, P.A., 1997. Recommendations for probabilistic seismic hazard analysis:

ering and Design 259 (2013) 222– 229 229

guidance on uncertainty and use of experts. U.S. Nuclear Regulatory CommissionReport NUREG/CR-6372.

Campbell, K.W., Bozorgnia, Y., 2008. NGA ground motion model for the geometricmean horizontal component of PGA, PGV, PGD and 5% damped linear elasticresponse spectra for periods ranging from 0.01 to 10 s. Earthquake Spectra 24(1), 139–171.

Electrica Power Research Institute (EPRI), 1986. Seismic hazard methodology for thecentral and eastern United States, Electric Power Research Institute, TechnicalReport NP-4726.

Electric Power Research Institute (EPRI), 2006. Program on technology innovation:use of cumulative absolute velocity (CAV) in determining effects of small mag-nitude earthquakes on seismic hazard analysis. Technical Report 1014099.

Electric Power Research Institute (EPRI), 2007. Program on technology innovation:the effects of high frequency ground motion on structures, components, andequipment in nuclear power plants. Technical report 1015108.

Electric Power Research Institute (EPRI), 2008. Assessment of seismic hazard at 34U.S. Nuclear Plant Sites. Technical Report 1016736.

International Atomic Energy Agency (IAEA), 2007. Preliminary findings and lessonslearned from the 16 July 2007 earthquake at Kashiwazaki-Kariwa NPP. MissionReport, Vol. 1, Japan.

McGuire, R.K., 2004. Seismic Hazard and Risk Analysis. Earthquake Engineering andResearch Institute.

Musson, R. M. W., Northmore, S. L., Phillips, E., Boon, D., Long, D. McCue, K.,Ambraseys, N.N., 2006. The geology and Geophysics of the United Arab Emirates.Vol. 4: Geological Hazards, British Geological Survey, UK, 237 p.

Reiter, L., 1990. Earthquake Hazard Analysis. Columbia Univ. Press, New York.Rizzo, 2009. PSHA Analysis (Proprietary).Stepp, J.C., Wong, I., Whitney, J., Quittmeyer, R., Abrahamson, N., Toro, G., Youngs,

R., Coppersmith, K., Savy, J., Sullivan, T., 2001. Probabilistic seismic hazard anal-yses for ground motions and fault displacement at Yucca Mountain, Nevada.Earthquake Spectra 17 (1), 113–151.

United States Geological Survey (USGS), 2008. Documentation for the 2008Update of the United States National Seismic Hazard Maps. Open File Report2008-1128.

USNRC, 2007. Regulatory Guide 1.208, A Performance Based Approach to Define theSite Specific Earthquake Ground Motion. U.S. Nuclear Regulatory Commission.

Youngs, R.R., Coppersmith, K.J., 1985. Implications of fault slip rates and earth-quake recurrence models to probabilistic seismic hazard estimates. Bulletin ofSeismological Society of America 75 (4), 939–964.

Dr. Fernandez has 11 years of experience in civilengineering and is currently vice president of PowerGeneration Projects with Paul C. Rizzo Associates,Inc. He obtained his Ph.D. in civil and environmentalengineering from Carnegie Mellon University.His civilengineering experience has combined the disciplinesof geotechnical engineering and computational simula-tion of civil engineering infrastructure, seismic analysis,and soil–structure interaction analysis. He has directedgeotechnical investigations for the sitting of power gener-ation projects, including nuclear power plants and simpleand combined cycle generation units. His research activ-ities and doctorate work have focused on soil–structure

and soil–structure–soil interaction of urban regions and other infrastructure facili-ties.

Dr. Fatehi has 9 years of experience in earthquake andengineering seismology, and is currently a senior seis-