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Joint IAEA-KINS: Workshop on Siting Evaluation for Nuclear Facilities on 16-20 April 2018 in Korea
Seismic Hazards
Hoseon Choihoseon@kins.re.kr
Korea Institute of Nuclear Safety
Korea Institute of Nuclear Safety
CONTENTS
I. Earthquake Fundamentals
II. Earthquake Monitoring in KINS
III. Seismic Safety of NPP site in Korea
IV. IAEA Specific Safety Guide No. SSG-9
V. Remarks
1
Korea Institute of Nuclear Safety
• Seismic hazard vs. Seismic risk
– seismic hazard: a natural phenomenon such as ground shaking, fault
rupture, or soil liquefaction that is generated by an earthquake
– seismic risk: the probability that humans will incur loss or damage to
their built environment if they are exposed to a seismic hazard
• seismic risk = seismic hazard × vulnerability
2http://www.efehr.org
Korea Institute of Nuclear Safety
I. Earthquake Fundamentals
• From seismic source to ground motion
3
seismic source
path
site
ground motion
Modified Boore (1999)
Korea Institute of Nuclear Safety
• MW 7.8 Tangshan earthquake on July 28, 1976
– casualties: 242,769~700,000 dead
4
http://www.drgeorgepc.com
wikipedia
Korea Institute of Nuclear Safety
• MW 6.9 Great Hanshin (Kobe) earthquake on January 17, 1995
– casualties: 5,502~6,434 dead
5
http://www.alamy.com
wikipedia
Korea Institute of Nuclear Safety
• MW 9.1 Indian Ocean earthquake on December 26, 2004
– casualties: 230,000~280,000 dead and more missing
6
http://highered.mheducation.comhttp://www.sheppardsoftware.com
Korea Institute of Nuclear Safety
• MW 7.9 Sichuan earthquake on May 12, 2008
– casualties: 87,587 dead and 18,392 missing
7
wikipedia
http://agnesngoy.blogspot.kr
Korea Institute of Nuclear Safety
• MW 7.0 Haiti earthquake on January 12, 2010
– casualties: 100,000~316,000 dead
8
wikipedia
http://haitiearthquake.web.unc.edu
Korea Institute of Nuclear Safety
• MW 9.1 Tohoku earthquake on March 11, 2011
– casualties: 15,894 dead and 2,562 missing
9
wikipedia
http://agnesngoy.blogspot.kr
wikipedia
Korea Institute of Nuclear Safety
• MW 9.1 Tohoku earthquake on March 11, 2011
– Fukushima Daiichi nuclear disaster
10
http://www.dailymail.co.uk
http://www.dailymail.co.uk
Korea Institute of Nuclear Safety
• MW 7.8 Nepal earthquake on April 25, 2015
– casualties: 8,857 dead
11
wikipedia
http://www.abc.net.au
Korea Institute of Nuclear Safety
• World seismicity
12
http://www.sftext.com
Korea Institute of Nuclear Safety
• World seismicity
13
http://ds.iris.edu/seismon/
Korea Institute of Nuclear Safety
• The largest earthquakes: top 10
14
USGS
Korea Institute of Nuclear Safety
• Once upon a time in Japan …
15
http://www.madeinslant.com
Korea Institute of Nuclear Safety
• Earthquake
– definition: both sudden slip on a fault, and the resulting ground
shaking and radiated seismic energy caused by the slip, or by
volcanic or magmatic activity, or other sudden stress changes in the
earth
– aftershock: a small earthquake that follows the main earthquake
– foreshock: a small earthquake that often precedes a major
earthquake
16
Korea Institute of Nuclear Safety
• Elastic rebound theory
– the first theory to satisfactorily explain earthquakes
17
https://myprojectwiki.wikispaces.com
Korea Institute of Nuclear Safety
• Stress and earthquake
– stress changes and earthquake sequence
18
http://iopscience.iop.org
Korea Institute of Nuclear Safety
• Causes of earthquakes
– natural: tectonic, volcanic, meteorite, ice-quake
– artificial: explosion
– etc.: collapse
19
http://www.lanl.gov
Korea Institute of Nuclear Safety
• Earthquake and fault
– MS 8.0 Mino-Owari (Nobi) earthquake on October 28, 1891:
documented the comprehensive fault breaks visible on the surface
20
http://www.meijishowa.com
wikipedia
Korea Institute of Nuclear Safety
• Earthquake and fault
– MW 6.9 Great Hanshin (Kobe) earthquake on January 17, 1995
21
wikipedia http://home.hiroshima-u.ac.jp
Korea Institute of Nuclear Safety
• Earthquake and fault
– earthquake history of Southern California
22
http://www.drtoddfrench.com
Korea Institute of Nuclear Safety
• Fault
– a fracture along which the blocks of crust on
either side have moved relative to one another
parallel to the fracture
23
USGS
https://www.slideshare.net
https://www.geo.uu.nl
Korea Institute of Nuclear Safety
• Plate tectonics
– supported by a wide range of evidence that considers the earth's
crust and upper mantle to be composed of several large, thin,
relatively rigid plates that move relative to one another
24
http://geology.com
wikipedia
Korea Institute of Nuclear Safety
• Seismic belt
– circum-Pacific belt (Ring of Fire): 75% of the world’s seismic energy
– plate boundary: 95% of the world’s seismic energy
25
wikipedia
Korea Institute of Nuclear Safety
• Intraplate earthquake
– not occur near plate boundaries, but along faults in the normally
stable interior of plates
– present a weakness in the crust where it can easily slip to
accommodate regional tectonic strain
26wikipedia
Korea Institute of Nuclear Safety
• Earthquake size
– magnitude: a number that characterizes the relative size of an
earthquake based on measurement of the maximum motion
recorded by a seismograph
– intensity: a number (written as a Roman numeral) describing the
severity of an earthquake in terms of its effects on the earth's surface
and on humans and their structures
27
KMA https://www.flickr.com
Korea Institute of Nuclear Safety
• Magnitude
– measure of the energy released by an earthquake
• independent of distance
– measured by seismographs
• objective and quantitative
– different magnitudes for different seismic waves
• ML (local magnitude) is well-known (also known as the Richter magnitude)
• mb (body wave), MS (surface wave), MW (seismic moment) …
28http://geoadvanced.com
Korea Institute of Nuclear Safety
• Richter magnitude
– developed in 1935 by Charles F. Richter of
the California Institute of Technology as a
mathematical device to compare the size of
earthquakes
– defines magnitude as the logarithm of the
ratio of the amplitude of the seismic waves
to an arbitrary, minor amplitude, as
recorded on a standardized seismograph at
a standard distance
– ML = log10A – log10A0
– energy vs. magnitude: 101.5*ΔM
• ML 4.5 vs. ML 6.5 ☞ energy difference?
29
wikipedia
http://www.ux1.eiu.edu
Korea Institute of Nuclear Safety
• Moment magnitude
– seismic moment (M0): a measure of the size of
an earthquake based on the area of fault
rupture, the average amount of slip, and the
force that was required to overcome the
friction sticking the rocks together that were
offset by faulting
– MW = 2/3 log10(M0) – 10.7 (H. Kanamori)
30
USGS
http://www.gps.caltech.edu
Korea Institute of Nuclear Safety
• Fault size vs. Magnitude
– fault dimension (length, displacement, area) in a particular
earthquake correlates with the magnitude of the earthquake
31
https://www.slideshare.net
Korea Institute of Nuclear Safety
• Magnitude vs. Frequency
– Gutenberg-Richter law: the relationship
between the magnitude and total number of
earthquakes in any given region and time
period of at least that magnitude
– log10N = a – b*M
• N: number of events ≥ M
• a: productivity
• b: b-value
32
USGSKHNP
Korea Institute of Nuclear Safety
• Intensity
– grades of the severity of earthquake impact
• natural phenomena, damage to man-made structures, human’s sensation
– basically a subjective and qualitative measure
– subject to site and structure conditions
• soil condition, groundwater level, slope of ground
• height, aging, material of structures
– various intensity scales have been developed
• JMAI (Japan), MMI (US), MSKI (Europe), etc.
– increasing as decreasing distance
• if the intensity is to be used as a measure of earthquake size, it should be
evaluated at a reference point, e.g., at the epicenter
33
Korea Institute of Nuclear Safety
• Modified Mercalli Intensity (MMI)
34
https://www.quora.com
Korea Institute of Nuclear Safety
• Magnitude vs. Acceleration vs. Intensity
– Gutenberg and Richter
• M = 2/3*Ie + 1.0
• log a = Ie/3 – 1/2
– USGS
• ShakeMap
35
KINShttp://crack.seismo.unr.edu
Korea Institute of Nuclear Safety
• Location
– hypocenter: point within the earth where an earthquake rupture starts
• latitude, longitude, depth
– epicenter: point on the earth's surface vertically above the
hypocenter
• latitude, longitude
36
http://www.seismo.ethz.ch
Korea Institute of Nuclear Safety
• Location
– use the fact that P and S waves travel at
different speeds to locate earthquakes (S-P
time)
– distance = S-P time * VP * VS / (VP – VS)
• S-P time = 8 sec; VP = 8 km/sec;
VS = 4 km/sec
• distance = ?
– need at least 3 seismic stations
• Origin time
– time at which an earthquake begins
– standardized time (UTC), local time (e.g. KST)
37
http://eqseis.geosc.psu.edu
Korea Institute of Nuclear Safety
• Focal depth
– shallow: 0 km~70 km
– intermediate: 70 km~300 km
– deep: 300 km~700 km
38
https://earthquakesandplates.wordpress.com
Korea Institute of Nuclear Safety
• Seismic wave
– an elastic wave generated by an impulse such as an earthquake or
an explosion
– travel either along or near the earth's surface (Rayleigh and Love
waves) or through the earth's interior (P and S waves)
39
http://web.ics.purdue.edu
Korea Institute of Nuclear Safety
• Seismic wave
– P wave (primary, compressional): seismic body wave that shakes the
ground back and forth in the same direction and the opposite
direction as the direction the wave is moving
– S wave (secondary, shear): seismic body wave that shakes the
ground right and left perpendicular to the direction the wave is
moving
40USGS
wikipedia
Korea Institute of Nuclear Safety
• Seismic wave
– Rayleigh wave: seismic surface wave causing the ground to shake in
an elliptical motion, with no transverse, or perpendicular, motion
– Love wave: surface wave having a horizontal motion that is
transverse (or perpendicular) to the direction the wave is traveling
41
USGS
Korea Institute of Nuclear Safety
• Components of seismic wave
– phase velocity (propagation)
– group velocity (modulation, envelope)
– amplitude
• measurement of particle motion in the medium
• half of the difference between max and min: ½ of peak-to-peak
• peak amplitude: absolute max amplitude
• conventional unit of peak acceleration: g (gravity)
42
wikipedia
Korea Institute of Nuclear Safety
• Components of seismic wave
– period, T: the time spent for one cycle (snap shot)
– wavelength, λ: the distance required for one cycle (seismogram)
– frequency, f: no. of cycles per second
– phase velocity: V = f × λ
43
http://bomeelectricity.blogspot.kr
Korea Institute of Nuclear Safety
• Seismic attenuation
– origins
• geometrical spreading: analogous to fading out of light
• inelastic attenuation: loss of energy due to medium defects
• scattering: due to medium heterogeneity, most significant at the near
surface
– typical form: ground motion prediction equation
• ln a = c1 + c2M + c3Mc4 + c5ln[r + c6exp(c7M)] + c8r + f(source) + f(site)
with δlna = c9
44https://www.slideshare.net
Korea Institute of Nuclear Safety
• Distance
– fault source
• rjb, rrup, rseis
– point source
• rcent, rhyp, repi
45
http://www.ce.memphis.edu
Korea Institute of Nuclear Safety
• Earthquake damage
– earthquake damage varies according to distance, region, etc. even if
earthquake sizes are same
– other causes?
• duration
• soil type
• seismic design
• liquefaction
• tsunami …
46
http://framework.latimes.com
Korea Institute of Nuclear Safety
• Earthquake damage
– duration: a strong influence on earthquake damage
• even if the amplitude of the motion is high, short duration may not
produce enough load reversals for damaging response to build up in a
structure
• related to the time required for release of accumulated strain energy by
rupture along the fault
• bracketed duration is most commonly used
47
https://www.researchgate.net https://www.slideshare.net
Korea Institute of Nuclear Safety
• Earthquake damage
– soil type: according to the soil type, the degree of site amplification is
different
• site effects by MW 8.0 Mexico City earthquake on September 19, 1985
48
http://www.wikiwand.com http://www.mexiconewsnetwork.com
Korea Institute of Nuclear Safety
• Earthquake damage
– seismic design, seismic isolation, seismic control
49
http://hncblog.com
Korea Institute of Nuclear Safety
• Earthquake damage
– liquefaction
• refers to the process by which water-saturated, unconsolidated
sediments are transformed into a substance that acts like a liquid, often
in an earthquake
50
wikipedia
http://civilarc.com
Korea Institute of Nuclear Safety
• Earthquake damage
– tsunami
• a series of waves in a water body caused by the displacement of a large
volume of water, generally in an ocean or a large lake
• earthquakes, volcanic eruptions and other underwater explosions
(including detonations of underwater nuclear devices), landslides, glacier
calvings, meteorite impacts and other disturbances above or below water
all have the potential to generate a tsunami
51
wikipedia
Korea Institute of Nuclear Safety
• Earthquake damage
– Spatial distribution of tsunami height by Tohoku earthquake on
March 11, 2011
52
http://www.coastal.jp
Korea Institute of Nuclear Safety
• Earthquake prediction
– concerned with the specification of the time, location, and magnitude
of future earthquakes within stated limits, particularly the
determination of parameters for the next strong earthquake to occur
in a region
– but, most scientists are pessimistic and some maintain that
earthquake prediction is inherently impossible
– MS 7.3 Haicheng earthquake on February 4, 1975
• observation of significant increase of micro-earthquakes → evacuation of
people → 2,041 killed (predicted casualty: more than 150,000) → the
most widely cited success of earthquake prediction
53http://www.thatsmags.com
wikipedia
Korea Institute of Nuclear Safety
• Seismograph
– instrument used to detect and record earthquakes
– generally refers to the seismometer and its recording device as a
single unit
• seismic sensor: accelerometer, velocity sensor
• seismic recorder
• charger, battery, UPS, network equipment …
54
http://www.kinemetrics.com
wikipedia
http://www.blessthisstuff.com
Korea Institute of Nuclear Safety
• Global seismographic network
55
http://www.hko.gov.hk
Korea Institute of Nuclear Safety
• Seismic stations in South Korea
– KMA, KIGAM, KHNP, KINS …
56
Choi et al. (2016)
Korea Institute of Nuclear Safety
• GSHAP
57
Malaysia
Indonesia
Philippines
Bahrain
Thailand
Tunisia
Vietnam
IraqJordan
Sudan
South Korea
Kazakhstan
Burkina Faso
Republic of the Congo
Ethiopia
Gabon
Ghana
Kenya
Madagascar
Mali
Nigeria
Senegal
Republic of South Africa
Uganda
France
Morocco
Republic of Cote d'Ivoire
Korea Institute of Nuclear Safety
• The Korean Peninsula is
– located at the far eastern part of Eurasian Plate
– within the intra-plate region several hundred km away from the
nearest plate boundary
58
Choi et al. (2012)
Korea Institute of Nuclear Safety
• Seismicity in the Korean Peninsula
– low seismicity, relatively smaller magnitude than that of inter-plate
earthquakes, spatially irregular epicenters
• however, on September 12, 2016, the largest instrumental event (ML 5.8)
was occurred nearby Gyeongju area and the second largest event (ML
5.4) in Pohang followed in 2017.
59
KMA
Korea Institute of Nuclear Safety
• ML 5.8 Gyeongju earthquake on September 12, 2016
– the largest event during the modern instrumental
recording period (since 1978)
– followed by numerous aftershocks (~600)
60
Kim et al. (2016) Lee and Song (2016)
wikipedia
Korea Institute of Nuclear Safety
• ML 5.4 Pohang earthquake on November 15, 2017
– the second largest event after 2016 Gyeongju earthquake
– cause significant infrastructure damage in Pohang
– followed by many aftershocks (~99)
61
KMA
https://blog.naver.com/pohangfood/
wikipedia
Korea Institute of Nuclear Safety
• Tsunami around the Korean Peninsula
62
Satake (2007) KMA
Korea Institute of Nuclear Safety
• Focal mechanism
– describes the deformation in the source region that generates the seismic
waves
– also known as a fault-plane solution
63USGS
Korea Institute of Nuclear Safety
• Damage caused by tsunami in the Korean Peninsula
64
KINS
http://blog.naver.com/
Korea Institute of Nuclear Safety
II. Earthquake Monitoring in KINS
• History
– government proclamation of earthquake preparedness measures (1997)
– deployment of seismic network (1998)
– opening of earthquake monitoring center (2001)
• Mission
– monitoring earthquake ground motions at nuclear facility sites
– analyzing characteristics of Korea earthquakes
– evaluating earthquake damages to nuclear structures
65
KINS
Korea Institute of Nuclear Safety
• Observation
– located at nuclear facility sites
– sensors and recorders
– ground motion recording & transmission
66
KINS
Korea Institute of Nuclear Safety
• Monitoring center
– located at KINS
– communication equipment
& computers
– data gathering & analysis
67
KINS
Korea Institute of Nuclear Safety
• Recordings of Gyeongju earthquake on September 12, 2016
– where is the closest station from the event? why?
68
KINS
49
148
26
254
Korea Institute of Nuclear Safety
• Recordings of Pohang earthquake on November 15, 2017
– where is the farthest station from the event? why?
69
KINS
88
107
46
278
Korea Institute of Nuclear Safety
III. Seismic Safety of NPP site in Korea
• World seismicity and nuclear power plants
70http://maptd.com
Korea Institute of Nuclear Safety
• Seismic preparedness step
71
Site Selection• Existence of capable fault
• Appropriateness of design earthquake
Construction• Appropriateness of seismic qualification on-site
• Inspection of seismic monitoring system (SMS)
Operation• Regular inspection
• Operation of earthquake monitoring network
Design• Appropriateness of seismic design
• Inspection of seismic qualification
• Regional and site investigation on geologic and
seismic characteristics
• Geology, seismology, geotechnical engineering
• Seismic design and qualification of the safety-
related SSCs* by dynamic analysis and test
• Seismic design engineering, structural engineering
• Inspection of seismic qualification (the safety-related
SSCs)
• Inspection of installation and capacity of SMS
• Regular inspection of SMS
• Check of the seismic safety of the safety-related
SSCs against earthquakes`
* SSCs: structures, systems and components
Korea Institute of Nuclear Safety
• Emergency response procedure
72
Earthquake
PGA ≥ 0.01 g
PGA ≥ 0.1 g
PGA ≥ design eq.
• Announcement of an alarm
• Shutdown of a nuclear reactor
• Announcement of facility
emergency
• Radiation emergency plan
• Restart of a nuclear reactor
• Check the safety-related
SSCs
• Restart of a nuclear reactor
• Shutdown of a nuclear reactor
• Announcement of site area
emergency
Korea Institute of Nuclear Safety
• Again
– from seismic source to ground motion
– if we can characterize seismic sources (e.g., faults), paths (e.g.,
crustal structures), and sites (e.g., subsurface) …
• it is possible to predict the maximum ground motion at the site
• design earthquake ground motion can be determined
73
seismic source
path
site
ground motion
Modified Boore (1999)
Korea Institute of Nuclear Safety
• Design Earthquake (ground motion)
– safe shutdown earthquake (ground motion) (SSE)
• seismic design for safety related SSCs
• at least 0.1g in peak ground acceleration
• SL-2 in IAEA terminology
– operating basis earthquake (ground motion) (OBE)
• seismic design for continuous operation
• SL-1 in IAEA terminology
– construction
• DE (ground motion) should be given in response spectra
74
Korea Institute of Nuclear Safety
• Response spectrum
– a plot of maximum responses of structures
of single-degree of freedom, in terms of
their natural frequencies
– representation of a structure by a simple
pendulum (single degree of freedom)
• pendulum mass (M) = sum of mass of
structure and attached facilities
• spring (k) = (shear) walls
• damping (c) = inelastic characteristics of
structure
– response spectra are provided for various
damping values of interest
– three types of response spectra
• (relative) displacement response spectra
• (relative) velocity response spectra
• (absolute) acceleration response spectra
75
https://www.linkedin.com
Korea Institute of Nuclear Safety
• Response spectrum
– tripartite chart
76
Moon et al. (2011)
Korea Institute of Nuclear Safety
• Related domestic regulations
– nuclear safety act
– regulations on technical standards for nuclear reactor facilities, etc.
• article 4 (geological features and earthquakes)
– notice of the Nuclear Safety and Security Commission No. 2014-10
(Technical standards for locations of nuclear reactor facilities)
• applicable foreign regulations: 10 CFR Part 100 Appendix A (Seismic and
Geologic Siting Criteria for Nuclear Power Plants)
– regulation criteria, regulation guide, safety review plan …
77
Korea Institute of Nuclear Safety
• Determination of DE in South Korea
– domestic regulation follows pre-revision version of US federal law
• deterministic method
• 10 CFR Part 100 Appendix A
– revision of US federal law on January 10, 1997
• probabilistic method
• 10 CFR Part 100 Subpart B 100.23
– current
• evaluation of DE by deterministic method
• appropriateness of DE by probabilistic method
78
Korea Institute of Nuclear Safety
• Procedures for determining DE
79
Collection and analysis of past earthquakes within a radius of 320 km from a site
- historical and instrumental earthquakes
- magnitude, depth, distance, recurrence interval
- seismic characteristics, focal mechanism, etc.
Analysis of relationships between past earthquakes and tectonic structures
- faults, folds, etc.
Establishment of seismotectonic provinces within a radius of 320 km from a site
Capable faults considered in design earthquake
Ground motions at a site from each seismotectonic province and capable fault
- ground motion prediction equations
- ground motion simulation
Site response analysis at a site
Controlling earthquake and design earthquake
Appropriateness of DE by probabilistic seismic hazard analysis
Determination of DE of a site
Korea Institute of Nuclear Safety
• Investigation of geosciences data
– geologic data
• identification of capable structures: faults, folds, etc.
– seismic data
• historical earthquakes: historical documents
• instrumental earthquakes: since 1900
• site-specific earthquakes: local seismic network
– check: reliability, accuracy, completeness
80
Korea Institute of Nuclear Safety
• Regional seismotectonic models
– general considerations
• seismic, geological, and geophysical data are combined to establish
regional seismotectonic models.
• it is not desirable to establish seismotectonic models that are more
sophisticated than the data support.
– seismic source
• capable tectonic structure
definition: a geological structure capable of generating earthquakes
characterization: location & geometry of geological structure, maximum
potential earthquake, earthquake recurrence rate, etc.
• seismotectonic province
definition: a region where earthquakes diffusely occur, but no specific geological
structure is identified to be responsible for those earthquakes.
characterization: similar to that of capable tectonic source
81
Korea Institute of Nuclear Safety
• Seismic source
– capable tectonic source (capable fault)
• 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
• macro-seismicity instrumentally determined with
records of sufficient precision to demonstrate a direct
relationship with the fault
• a structural relationship to a capable fault according
to characteristics above mentioned items of this
paragraph such that movement on one could be
reasonably expected to be accompanied by
movement on the other
– seismogenic source (seismotectonic province)
• cover a wide range of seismotectonic conditions,
from a well-defined tectonic structure to simply a
large region of diffuse seismicity
82
KHNP
Korea Institute of Nuclear Safety
• Capable fault
– design against
• vibratory ground motions
• surface deformation
83
capable fault
vibratory ground motion surface deformation
seismic safety
(design earthquake)
integrity of foundation
(site suitability/layout)
Korea Institute of Nuclear Safety
• Capable fault
– for faults, any part of which is within 320 km of the site and which
may be of significance in establishing DE
– minimum length of fault to be considered versus distance from site
84
distance (km) minimum length (km)
0~32 1.6
32~80 8
80~160 16
160~240 32
240~320 64
Korea Institute of Nuclear Safety
• Capable fault
85
evaluating
earthquake potentialextending to plant?
yes
no
capable fault
unsuitable
site
determining
design earthquakes
eng. solution
exists?
suitable
site
yes
no
Korea Institute of Nuclear Safety
• DE considering of near fault
– in the case where a causative fault is near the site, the effect of
proximity of an earthquake on the spectral characteristics of DE shall
be taken into account
86
Noh and Choi (2007) Jo (2006)
Korea Institute of Nuclear Safety
• Ground motion prediction equation
– a prediction equation for seismic ground motion
attenuation from seismic source to a site
– basic parameter: magnitude and distance
• faulting type: thrust, normal, strike-slip, etc.
• seismic wave transmission: soil, rock, etc.
– consideration of scattering
– various types of ground motion
• maximum ground acceleration, velocity, displacement
• response spectral acceleration, velocity,
displacement
– domestic status
• past poor seismic stations
• absence of large sized earthquake (strong ground
motion)
87
Noh and Choi (2007)
Korea Institute of Nuclear Safety
• Seismic wave transmission
– ground motions at the site should be corrected for those effects of
• seismic properties of plant site different from those of recording sites
• layered structures of underground materials of the plant site
• significant topography around the plant site
– design earthquake
• the maximum site ground motions corrected for wave transmission
characteristics
– NPP site in South Korea
• located on the basis rock
• composed of competent material
88KHNP
Korea Institute of Nuclear Safety
• Seismic hazard/design earthquakes
– deterministic & probabilistic methods
– Korean regulation requires the deterministic method: mean annual exceeding
frequency of SSE should be less than 1.0E-3
• Deterministic approach
– step
• establish a seismotectonic model consisting of capable tectonic
structures and seismotectonic provinces (i.e., seismic sources)
• determine the max. potential earthquake (MPE) for each seismic source
• locate each MPE at the closest point to site
• calculate the site ground motion by each MPE by using proper ground
motion prediction equation
• take the largest ground motion among all MPEs (max. site ground motion)
89
Korea Institute of Nuclear Safety
• Deterministic approach (diagrammatic)
90
move
attenuation
move
move
attenuation
Choi et al. (2016)
Korea Institute of Nuclear Safety
• Probabilistic approach
– uncertainties are originally inherited in the seismic characteristics
since faulting and earthquakes are occurred at the deep part of the
Earth, but investigation and observation are generally performed at
the surface area
– step
• construct seismotectonic models in terms of seismic sources including
uncertainty in source boundary
• for each source, determine magnitude-frequency models and MPEs
including the associated uncertainties
• select proper attenuation equations including the uncertainties
• evaluate annual frequency of exceedance for various levels of ground
motions: mean, median, 15th-percentile, 85th-percentiles
91
Korea Institute of Nuclear Safety
• Probabilistic approach (diagrammatic)
92
Reactor
A1 A2
F2 F1
R
A3
Acc
eler
atio
n, a
a*
Distance, R
Increasingmagnitude mi
Korea Institute of Nuclear Safety
• Design earthquake by deterministic approach
– DE of NPPs in South Korea is determined to be
• 0.2g (in case of newly constructed NPPs is 0.3g) considering the MPE
ground motions and some safety margin
• ground motions and surface deformations caused by capable faults are
also considered in the seismic design of NPPs
• design earthquake are given in response spectra
93
KHNP
Korea Institute of Nuclear Safety
• Design earthquake by deterministic approach
– in the case where a capable fault is near the site, the maximum
ground motion from this fault does not affect the DE of the site
94
KHNP
Korea Institute of Nuclear Safety
• Check of the appropriateness of DE
– by probabilistic approach
• mean annual exceeding frequency of design earthquake of NPP sites in
South Korea is evaluated to be less than 1.0E-3, and it meets the criteria
of the related regulatory guides
95
KHNP
Korea Institute of Nuclear Safety
• Design earthquake by probabilistic approach
– current global tendency to determine design earthquake by
probabilistic approach
• regulatory researches on the assessment of design earthquake by
probabilistic approach are in progress, the reflection to NPP sites in
Korea or not will be judged after reviewing their applicability
• regulatory guide 1.208 (U.S.NRC): a performance-based approach to
define the site-specific earthquake ground motion
– before applying design earthquake by probabilistic approach, related
domestic regulations should be revised
96
U.S.NRC
Korea Institute of Nuclear Safety
• Seismic safety of NPP site in Korea
– Through data analysis on geological and seismological
characteristics of the region within a radius of 320 km from the site
and the detailed geological survey of the area within a radius of 8 km
from the site
• NPPs in Korea are believed to be safe enough against the maximum
potential earthquake ground motion
– However, September 12, 2016 event with magnitude 5.8 (ML) nearby
Gyeongju area, which is the largest instrumental one in South Korea
• no significant damage to NPPs, but utility shutdowned 4 units located
nearby the epicenter within 4 hours
– The second largest event (ML 5.4) in Pohang followed in 2017
• cause significant infrastructure damage in Pohang
– Establishment of short and long term plans for reinvestigation
earthquake causative faults nearby NPP sites and reassessment of
design earthquake are in progress.
97
Korea Institute of Nuclear Safety
• Research on seismic source characterization of the September
2016 earthquake for reevaluating seismic safety of nuclear power
plant sites (from April 2017 to December 2021)
– Identification of the active fault for the Gyeongju earthquake and its
seismic source characterization
– Estimation of the maximum ground motion for the adjacent nuclear
power plants (NPP)
– Establishment of the long-term monitoring/preparedness system for
seismic hazard
– Interpretation of 3-D fault structure at and around the focal area of
the Gyeongju earthquake
– Development of evaluation technique for seismic safety of NPP sites
considering the Gyeongju earthquake
98
Korea Institute of Nuclear Safety
• Research on seismic source characterization of the September
2016 earthquake for reevaluating seismic safety of nuclear power
plant sites
– Establishment of microearthquake monitoring system and
development of its management technique
99Ree (2017)
Korea Institute of Nuclear Safety
IV. IAEA Specific Safety Guide No. SSG-9
100IAEA
Korea Institute of Nuclear Safety
• Background
– seismic hazard curves and ground motion spectra for the
probabilistic safety assessment of external events
– feedback of information from IAEA reviews of seismic safety studies
for nuclear installations performed over the previous decade
– collective knowledge gained from recent significant earthquakes
– new approaches in methods of analysis, particularly in the areas of
PSHA and strong motion simulation
• Objective
– vibratory ground motion hazards, in order to establish the design
basis ground motions and other relevant parameters
– potential for fault displacement and the rate of fault displacement that
could affect the feasibility of the site or the safe operation of the
installation at that site
101
Korea Institute of Nuclear Safety
• Necessary information and investigations
– need a comprehensive and integrated database of geological,
geophysical and seismological information
– investigation of 4 spatial scales
• regional investigations (typically 300 km): maps at a scale of 1:500,000 or
larger
• near regional investigations (typically not less than 25 km): maps at a
scale of 1:50,000
• site vicinity investigations (typically not less than 5 km): maps at a scale
of 1:5,000
• site area investigations (typically one square kilometer): maps at a scale
of 1:500
102
greater details towards the site
Korea Institute of Nuclear Safety
• Seismological database
– prehistoric and historical earthquake data
• date, time and duration of the event
• location of the macroseismic epicenter
• estimated focal depth
• estimated magnitude, the type of magnitude and documentation of the
methods used to estimate magnitude
• maximum intensity
• isoseismal contours
• intensity of the earthquake at the site
• estimates of uncertainty for all of the parameters
• an assessment of the quality and quantity of data
• information on felt foreshocks and aftershocks
• information on the causative fault
103
Korea Institute of Nuclear Safety
• Seismological database
– instrumental earthquake data
• date, duration and time of origin
• coordinates of the epicenter
• focal depth
• all magnitude determinations
• observed foreshocks and aftershocks (dimensions and geometry)
• information that may be helpful in understanding the seismotectonic
regime
• macroseismic details
• asperity location and size
• estimates of uncertainty for each of the parameters
• information on the causative fault, directivity and duration of rupture
• records from both broadband seismometers and strong motion
accelerographs
104
Korea Institute of Nuclear Safety
• Seismological database
– project specific instrumental data
• a network of sensitive seismographs having a recording capability for
micro-earthquakes be installed and operated
• earthquake analysis in connection with seismotectonic studies of the near
region within and near such a network
• strong motion accelerographs within the site area
• appropriately and periodically upgraded and calibrated instrumentation
105
Korea Institute of Nuclear Safety
• Seismotectonic model
– two types of seismic source
• seismogenic structures that can be identified by using the available
database
• diffuse seismicity (consisting usually, but not always, of small to moderate
earthquakes) that is not attributable to specific structures identified by
using the available database
– earthquake catalogue
• selection of a consistent magnitude scale for use in the seismic hazard
analysis
• determination of the uniform magnitude of each event in the catalogue on
the selected magnitude scale
• identification of main shocks (i.e. declustering of aftershocks)
• estimation of completeness of the catalogue as a function of magnitude,
regional location and time period
• quality assessment of the derived data, with uncertainty estimates of all
parameters
106
Korea Institute of Nuclear Safety
• Seismotectonic model
– magnitude-frequency relationship
• including the maximum potential magnitude
– maximum potential magnitude
• upper limit of integration in a probabilistic seismic hazard calculation and
in the derivation of the magnitude–frequency relationship
• scenario magnitude in a deterministic seismic hazard evaluation
– paleoseismic study
• identification of seismogenic structures on the basis of the recognition of
effects of past earthquakes in the region
• improvement of the completeness of earthquake catalogues for large
events, using identification and age dating of fossil earthquakes
• estimation of the maximum potential magnitude of a given seismogenic
structure
• calibration of probabilistic seismic hazard analyses, using the recurrence
intervals of large earthquakes
107
Korea Institute of Nuclear Safety
• Evaluation of the ground motion hazard
– ground motion hazard
• should preferably be evaluated by using both probabilistic and
deterministic methods of seismic hazard analysis
• when both deterministic and probabilistic results are obtained,
deterministic assessments can be used as a check against probabilistic
assessments in terms of the reasonableness of the results
– uncertainty
• both aleatory and epistemic uncertainties should be taken into account
– ground motion prediction models: attenuation relationships
• be current and well established at the time of the study
• be consistent with the types of earthquake and the attenuation
characteristics of the region of interest
• match as closely as possible the tectonic environment of the region of
interest
• make use of local ground motion data where available
108
Korea Institute of Nuclear Safety
• Uncertainty
109
aleatory epistemic
natural variability modeling or knowledge uncertainty
not reducible reducible with more information
addressed through integration over
parameter distributionaddressed through use of a logic tree
https://www.slideshare.net
Korea Institute of Nuclear Safety
• Evaluation of the ground motion hazard
– ground motion prediction models: seismic source simulation
• fault geometry parameters (location, length, width, depth, dip, strike)
• macroparameters (seismic moment, average dislocation, rupture velocity,
average stress drop)
• microparameters (rise time, dislocation, stress parameters for finite fault
elements)
• crustal structure parameters, such as shear wave velocity, density and
damping of wave propagation (i.e. the wave attenuation Q value).
110
Korea Institute of Nuclear Safety
• Probabilistic seismic hazard analysis (PSHA)
– step
• evaluation of the seismotectonic model for the site region in terms of the
defined seismic sources, including uncertainty in their boundaries and
dimensions.
• for each seismic source, evaluation of the maximum potential magnitude,
the rate of earthquake occurrence and the type of magnitude–frequency
relationship, together with the uncertainty associated with each
evaluation
• selection of the attenuation relationships for the site region, and
assessment of the uncertainty in both the mean and the variability of the
ground motion as a function of earthquake magnitude and seismic source
to site distance
• performance of the hazard calculation
• taking account of the site response
– evaluation of the annual frequency of exceedance of a specified level
of ground motion at a site due to one or more seismic sources by
integrating over all relevant contributions
111
Korea Institute of Nuclear Safety
• Deterministic seismic hazard analysis (DSHA)
– step
• seismogenic structure
the maximum potential magnitude (MPM) should be assumed to occur at the
point of the structure closest to the site area of the nuclear power plant (NPP)
when the site is within the boundaries of a seismogenic structure, the MPM
should be assumed to occur beneath the site
• diffuse seismicity
the MPM in a zone that includes the site of the NPP should be assumed to
occur at some identified specific horizontal distance from the site
the MPM associated with zones in each adjoining seismotectonic province
should be assumed to occur at the point of the province boundary closest to the
site
• ground motion prediction equations (attenuation relationships or, in some
cases, seismic source simulations): should be used to determine the
ground motion that each of these earthquakes would cause at the site
• taking account appropriately of both aleatory and epistemic uncertainties,
and incorporating the site response
112
Korea Institute of Nuclear Safety
• Potential for fault displacement at the site
– a fault is considered capable
• it shows evidence of past movement or movements (such as significant
deformations and/or dislocations) of a recurring nature within such a
period that it is reasonable to conclude that further movements at or near
the surface may occur
• a structural relationship with a known capable fault has been
demonstrated such that movement of the one fault may cause movement
of the other at or near the surface
• the maximum potential magnitude associated with a seismogenic
structure is sufficiently large and at such a depth that it is reasonable to
conclude that, in the current tectonic setting of the plant, movement at or
near the surface may occur
– site vicinity scale investigation
• very detailed geological and geomorphological mapping, topographical
analyses, geophysical surveys (including geodesy, if necessary),
trenching, boreholes, age dating of sediments or faulted rock, local
seismological investigations and any other appropriate techniques to
ascertain the amount and age of previous displacements
113
Korea Institute of Nuclear Safety
• Potential for fault displacement at the site
– probabilistic fault displacement hazard analysis (PFDHA)
• same procedures as are used to perform a probabilistic seismic hazard
analysis
• λ (D > d|t): the derived rate at which the surface or near surface fault
displacement D exceeds the value d in time t at the site
• P (D > d|m,r): the probability that the surface or near surface fault
displacement D exceeds the value d given an earthquake of magnitude m
on seismic source i located at a distance r from the site
• Levels of ground motion hazard
– SL-1
• corresponds to a less severe, more probable earthquake level that
normally has different implications for safety
– SL-2
• associated with the most stringent safety requirements
114
Korea Institute of Nuclear Safety
• Design basis response spectra
– site response analysis
• take into account the geological and geotechnical conditions at a site as
part of the estimation of ground motion
– uniform hazard response spectra
• selecting the values of the response spectral ordinates that correspond to
the annual frequencies of exceedance of interest from the seismic hazard
curves
– standardized response spectra
• having a smooth shape is used for engineering design purposes and to
account for the contribution of multiple seismic sources represented by
an envelope incorporating adequate low frequency and high frequency
ground motion input
115
Korea Institute of Nuclear Safety
V. Remarks
• Earthquake fundamentals
– provided basic knowledge about earthquake concept, principle,
phenomenon, etc. so as to enhance understanding of seismic
hazards
• Earthquake monitoring in KINS
– monitoring earthquake ground motions at nuclear facility sites
independently by regulatory institute
• Seismic safety of NPP site in Korea
– current global tendency to determine design earthquake by
probabilistic approach
• regulatory researches are in progress
• related domestic regulations will be revised
116
Korea Institute of Nuclear Safety
• Seismic safety of NPP site in Korea
– NPPs in Korea are believed to be safe enough against the maximum
potential earthquake ground motion
• however, short and long term plans for reinvestigation earthquake
causative faults nearby NPP sites and reassessment of design
earthquake are in progress after Gyeongju earthquake
• IAEA specific safety guide No. SSG-9
– vibratory ground motion hazards, in order to establish the design
basis ground motions and other relevant parameters
– potential for fault displacement and the rate of fault displacement that
could affect the feasibility of the site
117
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