Bogaazici Univerrsity,
K
Kandilli
Ob
bservatory aand Earthquake Researcch Institute
Depa
artment of Earthquak
ke Engineerring
The Occtober 23, 2011
2
Van, Turkey
T
Earrthquake (M
Mw=7.2)
PRO
OBABILIST
TIC ASSES
SSMENT O
OF THE SE
EISMIC HA
AZARD FO
OR THE LAKE
L
V
VAN BASIN
N
Introdu
uction
The seismic hazardd in Van Laake region iss retrieved from
f
the stu
udy of probaabilistic asssessment
of seism
mic hazard in Turkey conducted
c
ffor the Min
nistry of Traansportion T
Turkey, aim
ming the
preparaation of an earthquake
e
resistant deesign code for the construction off railways, seaports
and airpports (DLH, 2007).
Method
dology of PSHA
P
The genneral methoodology of calculatingg probabilisstic seismic hazard is well established in
literaturre (Cornell 1968). Th
he method involves tw
wo separatee models: a seismicity
y model
describiing a geogrraphical distribution evvent sources and the distribution oof magnitud
des, and
an attennuation moddel describiing the effeect at any site given ass a functionn of magnittude and
source-tto-site-distaance. The seeismicity m
model may comprise
c
a number of source regiions, the
seismiccity of which should bee expressedd in terms of a recurren
nce relationnship of eveents with
magnituudes greaterr or equal to
t a certain value. The attenuation
n model relaates the earrthquake
intensityy (i.e. the effect of itt, as a genneral term) at a site to
o magnitudde, distance, source
parametters and sitee conditionss.
For forrecasting seeismic occu
urrences num
merous models have been
b
develooped. The simplest
stochasttic model for
f earthquaake occurreences is the Homogeneeous Poissoon Model, which
w
is
used in this study. For the earrthquake eveents to follo
ow that mod
del, the folllowing assu
umptions
are in oorder:
1. Earthquakees are spatiaally indepenndent;
2. Earthquakees are tempo
orally indeppendent;
3. Probabilityy that two seeismic evennts will takee place at the same tim
me and at th
he same
place approoaches zero..
Obviouusly for the above assum
mptions to be applicab
ble to a dataa set, it shou
ould be free of foreand afteershocks. This
T
has beeen achievedd in our study by remo
oving all the
he dependen
nt events
from thhe earthquakke cataloguee.
The reccurrence reelationship of the eveents is exp
pressed witth the helpp of the em
mpirical
log
g
N

A

bM
b
relationnship first deefined by Gutenberg
G
-R
Richter:
where N is the nu
umber of
shocks with magnnitude greateer or equal to M per unit
u time an
nd unit areaa, and A an
nd b are
seismicc constants for any given
g
regionn. The sou
urce regions may be described as lines
represennting the knnown faultss or areas off diffuse seiismicity, so
o that M maay be related
d to unit
1
Bogaazici Univerrsity,
K
Kandilli
Ob
bservatory aand Earthquake Researcch Institute
Depa
artment of Earthquak
ke Engineerring
length oor unit areaa. The valuee of N will also generaally be foun
nd assumingg that M haas upper
and low
wer bounds M1
M and Mo
o.
Using aan applicatiion of the total
t
probabbility theoreem the prob
bability perr unit time that
t
that
ground motion ampplitude a* is exceeded can be exprressed as fo
ollows (McG
Guire, 1993):
PA  a * in time t / t   vi   GA
m, r
a * f m m f r r mdmdr
i
PI  i m, r 
is the prob
bability thatt the maxim
mum effect I is less than
an i. Given m and r,
where
f r m
f m m  is the probbability den
nsity functioon for magnitude, an
nd r
is the pro
obability
f r m
distribuution functioon for distan
nce. r
is dependeent on the geometric
g
naature of the source.
Seismicc Source Zoonation
mic source zone is deffined as a sseismically homogenous area, in which every point
A seism
within tthe source zone is assumed to haave the sam
me probabiliity of beingg the epicen
nter of a
future earthquake. An ideall delineatioon of seism
mic sourcee zones reqquires a complete
c
compreehension off the geolo
ogy, tectonnics, paleosseismology, historicall and instrrumental
seismiccity, and othher neotectonic featuress of the regiion under sttudy. Howevver, it is not always
possiblee to compille detailed informationn in all theese fields for
f the majoority of thee world.
Thus, ffrequently, seismic so
ource zonees are deteermined witth two funndamental tools; a
seismiccity profile and the teectonic reggime of thee region un
nder considderation. Although
A
seismicc source zonnation is a widely
w
usedd methodolo
ogy to deteermine earthhquake hazaard, it is
not the only approoach. Sincee delineatioon of the seismic sourrce zones sstill remain
ns rather
o
methhods for ev
valuating
subjectiive, researcchers (e.g. Frankel, 1 995) are suggesting other
seismicc hazard, inn order to eliminate thee subjectiviity of this procedure.
p
T
This is partticularly
importaant in areass where thee tectonic structure iss very fragmented andd the seism
micity is
diffuse. Whereas in
i most reg
gions of Tuurkey, the seismicity
s
is relativelyy well docu
umented,
major ffaults are often
o
well defined
d
andd the sourcce zones arre fairly obbvious. Hen
nce it is
consideered adequate to use thee conventioonal method
d of seismic source zonnation for Turkey in
this studdy.
The seiismic sourcce zonation used in thhis study is essentially
y based on the seismicc source
zonationn model of Turkey developed
d
w
within the context off a project conducted for the
Ministryy of Transpportion Turrkey, aiminng the prepaaration of an
a earthquaake resistan
nt design
code foor the consstruction off railways, seaports an
nd airports (DLH, 20007), which was an
updatedd version off the GSHA
AP (1999, E
Erdik et al. 1999) and
d TEFER (22000) models. The
main im
mprovemennt of the DLH
D
model when com
mpared to the previouus two mod
dels (the
GSHAP
P and TEFE
ER models)) was the reepresentatio
on of main fault
f
traces (such as th
he North
Anatoliian and thee East Anattolian Faultts) with lin
near sourcess. In order to accountt for the
spatiallyy more difffuse moderaate size seissmicity arou
und these faaults, widthss of at leastt several
kilometters were asssigned to th
he zones eveen if the asssociated fau
ults were weell expresseed on the
surface.. In the new
w model how
wever, earthhquakes witth magnitud
de > 6.5 havve been assumed to
2
Bogaazici Univerrsity,
K
Kandilli
Ob
bservatory aand Earthquake Researcch Institute
Depa
artment of Earthquak
ke Engineerring
take plaace on the linear zonees, whereass the smaller magnitude events aassociated with
w the
same faault have beeen allowed to take placce in the surrrounding laarger areal zzone. In add
dition to
these zoones, backgground zones have also been used in
i this modeel.
Figurre 1. Sourcee Zonation m
model used in the study
y of DLH (22007)
3
Bogaazici Univerrsity,
K
Kandilli
Ob
bservatory aand Earthquake Researcch Institute
Depa
artment of Earthquak
ke Engineerring
Earthq
quake Recu
urrence Rellationships
The em
mpirical reccurrence reelationship for earthq
quakes (Gu
utenberg annd Richter Model.
Richter, 1954) is as follows:
log N = a + b M
where N is the nuumber of th
he earthquaakes above the magnittude M in a given reg
gion and
within a given periiod and a an
nd b are reggression con
nstants. The Gutenbergg-Richter reccurrence
model hhas been exxtensively used
u
in manny seismicitty studies an
nd has alsoo been confiirmed to
hold forr micro-earrthquakes. The
T coefficiient a is a constant
c
thaat is dependdent on the location
and tim
me of the saample used and b repreesents a co
onstant thou
ught to be ccharacteristiic of the
region.
The eaarthquake catalogues
c
are often biased du
ue to incom
mplete repoorting for smaller
magnituude earthquuakes in earrlier periodss. Thus to fit
f the recurrrence relatiionship to a region,
one shoould choose among usin
ng
(1) a shhort sample that is comp
plete in smaall events orr
(2) a lonnger samplee that is com
mplete in larrger events or
(3) a coombinationn of the two
o data sets to complette the deficcient data th
thereby obtaaining a
homogeeneous dataa set.
A direcct attempt too fit these daata to a regrression relaationship maay result in quadratic or
o higher
order exxpressions to accomm
modate the iinherent biaas and inho
omogeneity of the dataa. In the
methodd used in thhis study, an
a artificiallly homogeeneous data set is sim
mulated thro
ough the
determiination of thhe period over
o
which tthe data in a given maagnitude grooup are com
mpletely
reportedd (Stepp, 19973).
The com
mputed recuurrence paraameters as w
well as the maximum
m
magnitudes
m
associated with the
source zzones are prresented in Table 1.
4
Bogaazici Univerrsity,
K
Kandilli
Ob
bservatory aand Earthquake Researcch Institute
Depa
artment of Earthquak
ke Engineerring
Table 11. Source Zo
one Informaation
Source Zon
ne No
Fa
ault Name
Mech
hanism
a
b
M min - Mmaks
Z34
5.0 – 6.7
Outside Zone
Z34
Nortth Anatolian
Fault Zone (NAF)
Right Laterral Strike Slip 5.0 0.8
6.8 – 7.9
Inside Zoone
Z39
Outside Zone
5.0 -6.9
Gok
ksun Fault ı
Left Lateraal Strike Slip
2.7 0.7
Z39
Outside Zone
7.0 – 7 .5
Z42
Left Lateraal Strike Slip
Outside Zone
Z42
4.6 0.9
5.0 – 6.7
A
Faullt
East Anatolian
Zo
one(EAF)
6.8 – 7.9
Inside Zoone
Z43
Outside Zone
Z43
_Zagros Faultt
Bitlis_
Zone
5.0 – 6.6
hrust
Th
4.7 1.0
Inside Zoone
Z46
6.7 – 7.0
North
N
East
Anaatolian Fault
Zone
Left and Right
R
Lateral
Strik
ke Slip
5.6 1.1
5.0 - 7.7
Z47
Pamb
baSevan Fault Right Lateraal Strike Slip +
Zone
3.9 0.9
Th
hrust
5.0 - 7.3
Z48
Tebriiz Fault Zone
5.0 - 7.3
Right Laterral Strike Slip 4.4 1.0
d Motion Prediction
P
Equations
E
Ground
Owing to the geological and geo-tectoniic similarity
y of Anatoliia to the Caalifornia (strike slip
faults similar to North,
N
North
heast and E
East Anatoliian Faults), the follow
wing ground
d motion
5
Bogaazici Univerrsity,
K
Kandilli
Ob
bservatory aand Earthquake Researcch Institute
Depa
artment of Earthquak
ke Engineerring
predictiion equationns currently
y being useed for the assessment of earthquuake hazard
d for the
Westernn US was uttilized:
1. Average off Boore, Jo
oyner and Fumal (1997), Sadigh
h et al.(19997), and Campbell
C
(2003) for Peak
P
Groun
nd Accelerat
ation (PGA)

Average off Boore et al. (1997), S
Sadigh et.al. (1997) and
d Campbell (1997) for Spectral
Acceleratioon (Ss and S1)
S
Hazard
d Results
The prresent analyysis has been conduucted for reeturn perio
ods of 4755 and 2,47
75 years
corresponding to 90%
9
and 98 % probabbilities of non-exceede
n
ence in 50 years respeectively.
The sellected grouund motion parameterrs of analyssis were th
he Peak Grround Acceeleration
(PGA), the Spectraal Accelerations (SA) at periods of
o 0.2 sec and
a 1 sec. A grid size of 0.05
by 0.055 was usedd. The earth
hquake locaation uncerttainty was taken
t
as 100 km. The standard
s
deviatioons in the attenuation functions were taken
n as given in the assoociated papeers. The
results are presented in Figurre 2 throughh Figure 7 in form of the mean oof the log normally
n
distribuuted results obtained from
f
compuutations witth the abov
ve attenuatiion relation
nships in
bedrockk conditionss.
The subb-province based
b
hazarrd result is aalso presented in Table 2.
Table 2. Haazard resultts for Tabannlı, Erciş, Muradiye
M
and
d Van-Merkkez districtss
Epicentra
al Location (Tabanlı)) Erciş Muradiye
e Van ‐ Merkez PGA
SA(T=0..2s)
SA(T=1..0s)
PGA
SA(T=0..2s)
SA(T=1..0s)
PGA
SA(T=0..2s)
SA(T=1..0s)
PGA
SA(T=0..2s)
SA(T=1..0s)
72
0.23
0.51
0.14
0.12
0.27
0.09
0.1
0.26
0.075
5
0.27
0.59
0.15
475
0.43
0.94
0.28
0.22
0.49
0.16
0.18
0.41
0.14
0.47
1.04
0.31
2475
0.64
1.42
0.46
0.34
0.76
0.26
0.29
0.65
0.22
0.7
1.56
0.51
6
Bogaazici Univerrsity,
K
Kandilli
Ob
bservatory aand Earthquake Researcch Institute
Depa
artment of Earthquak
ke Engineerring
Figgure 2. PGA
A for 10% prrobability oof exceedence in 50 yeaars (blue triaangle show
ws the
epicenter of the Vann earthquak
ke given by KOERI).
7
Bogaazici Univerrsity,
K
Kandilli
Ob
bservatory aand Earthquake Researcch Institute
Depa
artment of Earthquak
ke Engineerring
Figurre 3. SA (T=
=0.2s) for 10%
1
probabbility of exceeedence in 50
5 years (bllue triangle shows
the epicen
nter of the V
Van earthquaake given by KOERI).
8
Bogaazici Univerrsity,
K
Kandilli
Ob
bservatory aand Earthquake Researcch Institute
Depa
artment of Earthquak
ke Engineerring
Figurre 4. SA (T=
=1.0s) for 10%
1
probabbility of exceeedence in 50
5 years (bllue triangle shows
the epicen
nter of the V
Van earthquaake given by KOERI).
9
Bogaazici Univerrsity,
K
Kandilli
Ob
bservatory aand Earthquake Researcch Institute
Depa
artment of Earthquak
ke Engineerring
Figgure 5. PGA
A for 2% prrobability off exceedencce in 50 yeaars (blue triaangle showss the
epicenter of the Vann earthquak
ke given by KOERI).
10
Bogaazici Univerrsity,
K
Kandilli
Ob
bservatory aand Earthquake Researcch Institute
Depa
artment of Earthquak
ke Engineerring
Figuree 6. SA (T=0.2s) for 2%
% probabilitty of exceed
dence in 50 years (bluee triangle sh
hows the
epicenter of the Vann earthquak
ke given by KOERI).
11
Bogaazici Univerrsity,
K
Kandilli
Ob
bservatory aand Earthquake Researcch Institute
Depa
artment of Earthquak
ke Engineerring
Figure 7. SA (T=11.0s) for 2%
% probabilityy of exceed
dence in 50 years
y
(blue triangle sho
ows the
epicenter of the Vann earthquak
ke given by KOERI).
Site Specific Modification off Design Baasis Ground
d Motion
The connstruction of
o the design basis reesponse speectrum for different SSite Classess can be
achieveed through the
t modificcation of thee spectral acceleration
a
n (SA(0.2s) and SA(1ss)) given
by the hhazard mapps in Chaptter 6 or SEE
E and FEE
E level earth
hquakes. Thhe Uniform
m Hazard
Responnse Spectruum presenteed in NEH
HRP (2003, 2009) th
hat will be employed
d as the
approprriate spectraal shape is constructedd with two parameters: the site-sppecific shorrt period
(SMS); aand medium
m-period (SM1
hape of the spectrum
s
fo
or 5% dampping is illusttrated in
M ). The sh
Figure 88.
12
Bogaazici Univerrsity,
K
Kandilli
Ob
bservatory aand Earthquake Researcch Institute
Depa
artment of Earthquak
ke Engineerring
The sitte-specific short-period
s
d spectral rresponse accceleration parameter, SMS and mediumm
period pparameter SM1can be ob
btained as ffollows:
SMS = F
Fa * Ss
where Ss = SA(0.22s)
SM1 = F
Fv * S1
where S1= SA(1s))
Where Ss and S1 are
a represen
nted by the spectral accelerations at T=0.2 seec and T=1.0 sec at
referencce soil sitee (Vs,30 7
760m/s.) obbtained from
m the hazaard analysiis. Fa and Fv are
respectiively the applicable
a
Short
S
and Medium Period Amp
plification FFactors, deffined in
NEHRP
P (2003 andd 2009) (Tab
ble 3 and T
Table 4). The site classees indicatedd on these taables are
to be obbtained from
m the geo-teechnical invvestigations to be carrieed along thee pipeline ro
oute.
*TS: trannsition period from constantt response accceleration to constant respon
nse velocity, iin units of secconds, and
TL: traansition periodd from constan
nt response veelocity to consstant responsee displacement
nt, in units of seconds
s
Figuree 8. Standarrd Shape of the Respon
nse Spectrum
m (NEHRP,, 2009)
13
Bogaazici Univerrsity,
K
Kandilli
Ob
bservatory aand Earthquake Researcch Institute
Depa
artment of Earthquak
ke Engineerring
Tablle 3. Valuess of Fa as a function off Site Class and 0.2s Sp
pectral Acceeleration (att B/C
boundaryy with Vs = 760 m/s)
Site C
Class
Ss0.25
Ss=0.550
Ss=0.75
S
Ss=1.0
1.25
Ss
A
0.8
0.8
0.8
0.8
0.8
0
B
1
1
1
1
1
C
1.2
1.2
1.1
1
1
D
1.6
1.4
1.2
1.1
1
E
2.5
1.7
1.2
0.9
0.9
0
F
*
*
*
*
*
* Siite-specific geotechnical
g
investigationn and dynam
mic site respo
onse analysess shall be perrformed.
Tablle 4. Valuess of Fv as a function off Site Class and 1.0s Sp
pectral Acceeleration (at B/C
boundaryy with Vs = 760 m/s)
Site C
Class
Ss=0.200
Ss=
=0.3
Ss=0.4
S
Ss0.1
Ss0.5
A
0.8
0.8
0.8
0
0.8
0.8
B
1
1
1
1
1
C
1.7
1.6
1.5
1.4
1.3
D
2.4
2.0
1.8
1.6
1.5
E
3.5
3.2
2.8
2
2.4
2.4
F
*
*
*
*
*
* Site-specific geeo-technicall investigatioon and dynam
mic site respo
onse analyses
es shall be peerformed.
QTM b
based Site Dependent
D
Hazard Reesults
The QT
TM map baased site deependent annalysis has been
b
condu
ucted for ret
eturn period
ds of 72,
475 andd 2,475 yeaars correspo
onding to 500%, 10% an
nd 2 % probabilities oof exceedence in 50
years reespectively. The selecteed ground m
motion paraameters of analysis
a
werre the Peak Ground
14
Bogaazici Univerrsity,
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Ob
bservatory aand Earthquake Researcch Institute
Depa
artment of Earthquak
ke Engineerring
Accelerration (PGA
A), and the Spectral
S
Acccelerations (SA) at perriods of 0.22 sec and 1 sec. The
results are presenteed in Figure 9 throughh Figure 12 in form off the mean oof the log normally
n
distribuuted results obtained
o
fro
om computaations with the above GMPEs
G
in ssite conditio
ons.
Figuure 9. QTM based SA (T=0.2s)
(
forr 10% probaability of ex
xceedence in 50 years (blue
(
e
given by K
KOERI).
trianglle shows thee epicenter oof the Van earthquake
15
Bogaazici Univerrsity,
K
Kandilli
Ob
bservatory aand Earthquake Researcch Institute
Depa
artment of Earthquak
ke Engineerring
Figurre 10. QTM
M based SA (T=1.0s) foor 10% prob
bability of exceedence iin 50 years (blue
trianglle shows thee epicenter oof the Van earthquake
e
given by K
KOERI).
16
Bogaazici Univerrsity,
K
Kandilli
Ob
bservatory aand Earthquake Researcch Institute
Depa
artment of Earthquak
ke Engineerring
Figuure 11. QTM
M based SA
A (T=0.2s) fo
for 2% probaability of ex
xceedence in 50 years (blue
(
trianglle shows thee epicenter oof the Van earthquake
e
given by K
KOERI).
17
Bogaazici Univerrsity,
K
Kandilli
Ob
bservatory aand Earthquake Researcch Institute
Depa
artment of Earthquak
ke Engineerring
Figuure 12. QTM
M based SA
A (T=1.0s) fo
for 2% probaability of ex
xceedence in 50 years (blue
(
trianglle shows thee epicenter oof the Van earthquake
e
given by K
KOERI).
Contribbuted by: E.
E Çaktı, M.B.
M
Demirrcioğlu, M. Erdik, Y. Kamer, B. Sungay, E.
E Şafak,
K. Şeşeetyan, E. Uççkan, E. Vurran, C. Yennidoğan, C. Zulfikar
Z
(in
n alphabeticcal order)
18