türki̇ye ve ci̇varindaki̇ farkli si̇smi̇k bölgeler i̇çi̇n aletsel

TÜRKİYE VE CİVARINDAKİ FARKLI SİSMİK BÖLGELER İÇİN
ALETSEL VERİYE DAYALI DEPREM HAZARD PARAMETRELERİNİN
BİR DEĞERLENDİRMESİ
AN EVALUATION OF EARTHQUAKE HAZARD PARAMETERS BASED
ON THE INSTRUMENTAL DATA FOR DIFFERENT SEISMIC REGIONS
OF TURKEY AND ADJACENT AREAS
Yusuf Bayrak1, Serkan Öztürk1, Theodoros M. Tsapanos2, George Ch. Koravos2, Georgios
A. Leventakis2, Doğan Kalafat3
1
Karadeniz Technical University, Department of Geophysics, Trabzon, Turkey
2
Aristotle University of Thessaloniki, School of Geology, Geophysical Laboratory, Greece
3
Boğazici University, Kandilli Observatory and Earthquake Research Institute, İstanbul, Turkey
E-posta: bayrak@ktu.edu.tr
_______________________________________________________________
Anahtar Kelimeler: Türkiye, maksimum bölgesel magnitüd, ortalama aktivite oranı, K indeksi
ÖZ Bu çalışmada, maksimum olasılık yöntemi kullanılarak Türkiye ve civarı için
maksimum bölgesel magnitüd M̂ max ve ortalama aktivite oranı λ̂ gibi deprem hazard
parametrelerinin bir değerlendirmesi yapılmıştır. Ayrıca, deprem hazard seviyesi göreceli
deprem hazard ölçeğinin bir fonksiyonu olarak (K indeksi olarak tanımlanmıştır)
hesaplanmış ve her bir bölge için haritalanmıştır. Çalışmada kullanılan veri KOERI ve ISC
kataloglarından derlenmiştir. 7.50’den büyük en yüksek M̂ max değerleri Kuzey Anadolu
Fay Zonu boyunca ve Ege arkında bulunmuştur. 100’den büyük en yüksek λ̂ değerleri o
bölgelerdeki belirgin bir magnitüd değeri üzerindeki olayların sayısındaki artışa bağlı
olarak Sultandağı, Beyşehir ve Tatar faylarında, Bitlis Bindirme Zonunda ve Doğu Anadolu
Fay Zonunda hesaplanmıştır. Ayrıca, en büyük K indeksi 6’ya eşittir ve Kuzey Anadolu
Fay Zonunun orta kısmı ile Ege Arkında gözlenmiştir.
Key words: Turkey, the maximum regional magnitude, the mean activity rate, index K
ABSTRACT In this study, using the maximum likelihood method an evaluation of
earthquake hazard parameters such as the maximum regional magnitude,
M̂ max
, and the
mean activity rate, λ̂ , is made for Turkey and adjacent areas. The earthquake hazard
level is also calculated as a function of relative earthquake hazard scale (defined as an
index K) and is mapped for each region. The data used in this study is compiled from the
catalogues of KOERI and ISC. The largest M̂ max values greater than 7.50 are found in the
Aegean Arc and along the North Anatolian Fault Zone. The largest λ̂ values greater than
100 are computed in Sultandağı, Beyşehir and Tatar faults, Bitlis Thrust Zone, and East
Anatolian Fault Zone depending on the great number of events above a certain
magnitude per year in these regions. Also, the largest index K is equal to 6 and observed
in the middle part of North Anatolian Fault Zone and Aegean Arc.
INTRODUCTION
Numerous seismic hazard studies have been made in order to estimate the earthquake
hazard in Turkey using the statistical processing of the instrumental earthquake data
92
(Båth 1979; Erdik et al., 1999; Bayrak et al., 2005). Although many reports are known
that Turkish instrumental records are far from being incomplete for probabilistic approach
of seismic hazard, an effort is undertaken for such analysis in the present study. Thus,
we aimed to evaluate the earthquake hazard parameters such as the maximum regional
magnitude, M̂ max , the mean activity rate, λ̂ , and the relative earthquake hazard scale,
index K, for Turkey and adjacent areas.
DATA USED and METHOD
The earthquake data used in this study is compiled from the Boğaziçi University, Kandilli
Observatory and Earthquake Research Institute (KOERI) and the International
Seismological Center (ISC) and historical catalogue of KOERI. There are 2398 events
between 1900 and 1974 and 68478 events between 1974 and 2005. The catalogue is
uniform of surface magnidude (MS). The final data between the time interval 1900-2005
and shallow earthquakes (depth<60 km) including 69339 events are used for the
calculations. Analysis is carried out in a rectangular area limited by the co-ordinates 25oE
and 45oE in longitude and 33oN and 43oN in latitude. The seismic source zones considered
in this study are defined according as the major fault systems and seismicity of Turkey as
well as the studies and seismic source zones made by other authors (Erdik et. al., 1999;
Bayrak et al., 2005). Thus, Turkey was divided into 24 seismic regions. Figure 1 shows
the seismic regions with the tectonic structures and the epicenters of earthquakes in
Turkey from 1900 to 2005.
A large number of earthquake occurrence models are currently available for seismic
hazard estimation. One of the most popular components of the earthquake hazard
assessment is the appraisal of the maximum regional magnitude and the relative
earthquake hazard level of a specific region. In order to estimate the maximum regional
magnitude, M̂ max , it is used the method given by Kijko, (1988) while the mean activity
rate, λ̂ , is computed by the method proposed by Kijko and Sellevoll (1989; 1992), and
Kijko and Graham (1998). In order to classify the examined regions in groups, based on
their difference in the hazard level, we follow the technique used by Tsapanos (2001).
Regional variation maps of M̂ max value and K index are drawn with different grey scale
and shown in Figures 2 and 3, respectively.
43
42
20
Latitude (Degrees)
41
40
19
14
2
22
16
15
38
8
10
35
34
5
6
11
36
23
13
37
1
24
18
17
39
33
25
21
3
4
7
9
12
26
27
28
29
30
31
32
33
34
35
36
37
38
Longitude (Degrees)
93
39
40
41
42
43
44
45
Figure-1. Different source regions considered in this study together with the major
tectonic structures. Epicenter distributions of earthquakes of MS between 4.0 and
8.0 for the time period 1900-2005 are also shown.
43
42
20
Latitude (Degrees)
41
40
19
14
2
22
16
15
38
8
10
35
3
4
5
6
11
34
23
13
37
36
1
24
18
17
39
33
25
21
7
9
12
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
Longitude (Degrees)
Mmax >7.5
6.8<Mmax 7.5
5.6<Mmax 6.8
Figure-2. M̂ max (the maximum regional magnitude) values for different 24 seismic
source regions in Turkey and adjacent areas.
43
42
20
Latitude (Degrees)
41
40
19
14
2
22
16
15
38
8
10
35
34
5
6
11
36
23
13
37
1
24
18
17
39
33
25
21
3
4
7
9
12
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
Longitude (Degrees)
K=2
K=3
K=4
94
K=5
K=6
41
42
43
44
45
Figure-3. K index (relative hazard level) values for different 24 seismic source regions in
Turkey and adjacent areas.
CONCLUSIONS
In this study, an effort is made for the evaluation of earthquake hazard parameters such
as the maximum regional magnitude, M̂ max , mean activity rate, λ̂ , and relative
earthquake hazard scale, index K, for Turkey and adjacent areas. For this purpose, it is
used the different methods proposed by some authors. Turkey was divided into 24
different regions taking into account the different zonation studies made by several
authors for modeling of seismic hazard in Turkey, and plotting the existing tectonic
structure with the episantr distribution of earthquakes. The data used in this study
includes the instrumental period between 1900 and 2005 and taken from the Boğaziçi
University, Kandilli Observatory and Earthquake Research Institute and the International
Seismological Center and historical catalogue of KOERI. The catalogue has 2398 events
between 1900 and 1974 and 68478 events between 1974 and 2005. For the calculations,
it is used the shallow earthquakes (depth<60 km) including 69339 events between the
time interval 1900 and 2005 and the catalogue is homogeneous for MS. We used a
rectangular area limited by the co-ordinates 25oE and 45oE in longitude and 33oN and
43oN in latitude. The earthquake hazard parameters such as the maximum regional
magnitude and the mean seismic activity rate are estimated by the maximum likelihood
method for whole Turkey. Also, the earthquake hazard level is calculated as a function of
relative earthquake hazard scale (defined as an index K) and mapped for each seismic
region. Consequently, it is observed the largest M̂ max values greater than 7.50 in the
Aegean Arc and along the North Anatolian Fault Zone. The largest λ̂ values greater than
100 are computed in Sultandağı, Beyşehir and Tatar faults, Bitlis Thrust Zone and East
Anatolian Fault Zone depending on the great number of events above a certain
magnitude per year in these regions. Also, the largest index K is observed in the middle
part of North Anatolian Fault Zone and Aegean Arc. Thus, the distribution of hazard level
from region to region is informative and useful from a practical point of view.
REFERENCES
Båth, M., 1979, Seismic risk in Turkey; a preliminary approach, Tectonophysics, 54,
T9-T16
Bayrak Y., Yılmaztürk, A., and Öztürk, S., 2005, Relationships between fundamental
seismic hazard parameters for the different source regions in Turkey, Natural Hazards,
36, 445-462
Erdik, M., Alpay, B. Y., Onur, T., Sesetyan, K., and Birgoren, G., 1999, Assessment of
earthquake hazard in Turkey and neighboring regions, Annali di Geofisica, 42, 11251138
Kijko, A., 1988, Maximum likelihood estimation of Gutenberg-Richter b parameter for
uncertain magnitudes values, Pageoph., 127, 573-579
Kijko, A., and Sellevoll, M. A., 1989, Estimation of earthquake hazard parameters from
incomplete data files. Part I. Utilization of extreme and complete catalogs with different
threshold magnitudes, Bull. Seismol. Soc. Am., 79, 645-654
Kijko, A., and Sellevoll, M. A., 1992, Estimation of earthquake hazard parameters from
incomplete data files. Part II. Incorporation of magnitude heterogeneity, Bull. Seismol.
Soc. Am., 82, 120-134
95
Kijko, A., and Graham, G., 1998, ‘Parametric-historic’ procedure for probabilistic seismic
hazard analysis. Part I. Estimation of maximum regional magnitude mmax, Pageoph.,
152, 413-442
Tsapanos, T. M., 2001, Evaluation of the seismic hazard parameters for selected regions
of the world: the maximum regional magnitude, Annali Di Geofisica, 44, N.1
96