Ataturk dam induced seismicity esc2010
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Transcript of Ataturk dam induced seismicity esc2010
CORRELATION BETWEEN WATER LEVEL DECREASE IN ATATURK DAM, TURKEY
and Mw 5.0 EARTHQUAKE ON SEPTEMBER 3, 2008
Haluk EYİDOĞAN, Veli GEÇGEL and Zumer PABUÇCUe mail: [email protected]
The examination of earthquake triggering mechanism of Atatürk dam area, the space and time distribution of the epicenters and solutions of the fault mechanisms belonging to the earthquake occurred in September 3, 2008 (02:2 UTC, ML=5.2) and its aftershocks (ML=4.6 and ML=4.0), and their correlation with the surrounding tectonic structure.
OBJECTIVE
Atatürk Dam Features
• Atatürk Dam is on the Fırat (Euphrates) river and is the fourth biggest clay cored rock-fill dam in the world regarding water capacity and amount of electricity produced.
• The main features of the dam are as follows: Dam height – 170m; Crest length – 1670m; Crest level – 549m; Maximum base width – approx. 900m; Dam volume – 84 x 106m3; Reservoir volume – 48 km3; Resrvoir area- 817 km2; Installed capacity – 2400MW; Annual energy generation – 8100GWh.
• The maximum and minimum operation reservoir levels are 542m and 526m asl respectively.
Tectonic development of the area is
governed by convergence of the
Arabian and African Plates towards
the Anatolian Plate. The Atatürk Dam
is located at 50 km southeast of East
Anatolian Fault zone which is the
most prominent structural elements in
the region. Bozova Fault was issued
on the Active Fault Map of Turkey in
1992 and Geology Map of Turkey.
Right-lateral strike-slip Bozova Fault
is located 1.5 km south of the dam
and has a length of about 55-60 km
The dam was started to be filled following the year of 1989. The reservoir level reached 535m asl in March 1994 and has varied between 526m and 537m asl since then. The maximum and minimum operation reservoir levels are 542m and 526m asl, respectively.
Atatürk Dam site has no large seismic activity in historical periods. It was seen that the triggered earthquake activity, obtained from the Kandilli Observatory and Earthquake Research Institute (KOERI) database, was evidently increasing following the year of 1994. Although KOERI stations are distant and few in number, the frequency of the earthquakes increased rapidly since 1994 following the highest level of water reach in the dam.
2
2,5
3
3,5
4
4,5
5
01.0
1.19
85
01.0
1.19
86
01.0
1.19
87
01.0
1.19
88
01.0
1.19
89
01.0
1.19
90
01.0
1.19
91
01.0
1.19
92
01.0
1.19
93
01.0
1.19
94
01.0
1.19
95
01.0
1.19
96
01.0
1.19
97
01.0
1.19
98
01.0
1.19
99
01.0
1.20
00
01.0
1.20
01
01.0
1.20
02
01.0
1.20
03
01.0
1.20
04
01.0
1.20
05
01.0
1.20
06
01.0
1.20
07
01.0
1.20
08
Time
Mag
nitu
de
0
100
200
300
400
500
600
Wat
er L
evel
in M
eter
s
31.1
2.20
08
Missing Data ?
0
5
10
15
20
25
30
35
40
01.01.1992 01.01.1994 01.01.2000 01.01.2004 01.01.2006 01.01.2007 01.01.2008 31.05.2009
Time (Year)
Num
ber o
f St
atio
ns
0
5
10
15
20
25
30
35
40
Cum
ulat
ive
Num
ber o
f Sta
tions
Number of the earthquake stations present in the area of 1x1 degree
The number of the earthquake stations did not undergo a great change until the TURDEP project activities (Inan et al., 2007) started for the region. 30 seismic stations were installed in the region, mainly along the EAFZ. This helped to increase the accuracy of the EQ parameters for the activity around the dam.
Fault mechanism solutions of the earthquakes with a magnitude of ML≥ 4.0 and the seismicity in the time period
between 2007-2009 (TURDEP Project Database)
1 1.5 2 2.5 3 3.5 4 4.5 529-Nov-06
17-Jun-07
3-Jan-08
21-Jul-08
6-Feb-09
25-Aug-09
13-Mar-10
Time vs Magnitude (2007-2009)
0.00 0.20 0.40 0.60 0.80 1.000
1
2
3
4
5
Md vs RMS Residuals
Md
The water level decreased rapidly in the summer of 2007, did not increase in the 2008 winter because of insufficient rainfall, and decreased even more in the summer of 2008. On September 3, 2008, in the days when the total decrease was 6 m, an earthquake with a magnitude of Mw=5.0 (ML=5.2) occurred in the northeast of the body of the dam; and aftershocks were experienced following the earthquake.
01/0
1/20
07
01/0
3/20
07
01/0
5/20
07
01/0
7/20
07
01/0
9/20
07
01/1
1/20
07
01/0
1/20
08
01/0
3/20
08
01/0
5/20
08
01/0
7/20
08
01/0
9/20
08
01/1
1/20
08
01/0
1/20
09
01/0
3/20
09
01/0
5/20
09
01/0
7/20
09
01/0
9/20
09
01/1
1/20
091.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
525
526
527
528
529
530
531
532
533
534
535
536
537
3 September 2008Mw=5.0
Time
Magnitude
Wat
er L
evel
in M
eter
s
817 km2 x 6.25 mAmount of drawdown ≈ 5 billion ton
* The strike slip mechanism at the ATATÜRK DAM site is due to shear-slip long the existing fractures as a result of increased maximum or minimum principal stresses.
* Shear stress in the region is probably close to the rock-mass frictional strengths and that a small perturbation of the shear stress field triggered the magnitude 5.0 activity.
σ R =σL – σS
σ3σ1Water level
σ1>σ3
N
CONCLUSIONS
• Considering the stress changes caused by the mechanism characteristics of the September 3, 2008 earthquake, ambient stress distrubition in the region, the locations of the aftershocks, and drastic decrease in the water level, the earthquake occurred on September 3, 2008 was interpreted as a triggered earthquake
• It could be stated that fast and significant amount of water load decrease in the Ataturk Dam caused the exceeding of the critical tension level by changing the ambient NW-SE directioned compressional stress or NE-SW directioned tensional stress and finally caused an earthquake with a magnitude of Mw=5.0.
CONCLUSIONS
• No concrete conclusion was reached regarding the correlation of the triggered seismicity, consisting of September 3, 2008 earthquake and its aftershocks, with the active Bozova Fault.
• It should be pointed out that the possibility that new changes in the tectonic forces around the dam and in depths and pore pressure, due to the water level changes in significant amounts, would cause stress effects that would trigger the Bozova Fault should be evaluated. The Bozova Fault that is located significantly close to the body of the dam should be urgently and multi-dimensionally examined.
We would like to offer our acknowledgements to Turkish Directory of State Water Affairs (DSI) and TUBITAK Marmara Research Center-Institute of Earth and Marine Science (MRC-IEMS) for their support for data. Zumer Pabuccu and Onur Tan made contributions for the acquisition of raw data, Aylin Tan spent efforts to supply some articles and documents and Argun Kocaoglu helped in installing and compiling softwares on my computer.
THANK YOU