Bulletin of the Seismological Society of America, 92, 1, pp. 61–66, February 2002
Surface Rupture and Slip Distribution of the 12 November 1999 Du¨zce Earthquake (M 7.1), North Anatolian Fault, Bolu, Turkey by H. S. Akyu¨z, R. Hartleb, A. Barka, E. Altunel, G. Sunal, B. Meyer, and R. Armijo
Abstract
The 12 November 1999 earthquake (M 7.1) occurred on the Du¨zce fault, a splay of the North Anatolian fault in the Bolu basin approximately three months after the 17 August 1999 (M 7.4) earthquake. The surface rupture was 40 km long, and the maximum right-lateral offset was 500 Ⳳ 5 cm, averaging 300 cm. The 9 km of the westernmost part of the rupture along the southern margin of the Eften Lake had a 350-cm maximum vertical displacement (normal faulting), some of which was already ruptured during the 17 August 1999 event with few tens of centimeters. The surface rupture has a generally simple narrow deformation zone of 0.5–5 m, however, in some places, it widens to 50 m. Transtensional and transpressional structures were observed within releasing and restraining step-over areas respectively. The larger dextral offsets on some streams indicate previous events. The dextral slip measurements along the rupture reflect a symmetric distribution. The eastern connection of this rupture zone with the main trace of North Anatolian fault remains unclear because the Bakacak and Elmalik fault, which are connecting faults, had no surface rupture.
Introduction deficit in the aread. (3) the 17 August 1999 earthquake increased the failure stress on this segment (Hubert et al., 2000; Parsons et al., 2000). These two earthquakes are considered as a whole although the Du¨zce earthquake occurred later at the eastern continuation of the I˙zmit earthquake; they formed as a result of a westward migrating earthquake sequence that formed after the 1939 Erzincan earthquake (Fig. 1). The simple trace of the North Anatolian fault between Erzincan and Bolu splays into two strands westward beyond Bolu (Fig. 1). The
The 12 November 1999 Du¨zce earthquake (M 7.1; USGS, KOERI) occurred on the western part of North Anatolian fault nearly three months after the I˙zmit earthquake (M 7.4; USGS) and resulted in approximately 900 deaths and 3000 injuries. The Du¨zce earthquake somehow was expected (Barka, 1999) for three reasons: (1) this was the only segment that had not ruptured in this section of the North Anatolian fault; (2) the slip distribution of 1944, 1957, 1967, and August 1999 earthquakes (Barka, 1996; Barka et al., 1999) indicated that there was at least a 2- to 2.5-m slip
N
27
31
29
33
1951
Istanbul Bolu
Fig.2
Bursa
1953
41
39
BLACK SEA
1999b
1999a 1912
37
35
Amasya
Anatolian Fault North
1992
1949
1964
1967
1957
1944
1943
200 km
1942
1939 Erzincan Basin
Figure 1.
The westward migrating earthquakes since 1939 along the North Ana-
tolian fault.
61
1966
62
40˚ 45'
40˚ 46'
40˚ 47'
40˚ 48'
250
260
330
115
90
756
Yenidag H.
500; 130 v
Site 2
Çapayakbeyköy
250
Cayköy
Hacisuleymanbey
330; 35 v
separation.
Figure 2.
280
871
Türbe H.
370
795
Orta H.
370
M e n g e n c i k
45
310 275
579
Kestanelik H.
420
Simsir
12 m-offset stream
15
Gürcüler
Süleymanbey
40
110
75
Haciyakup
G Ö LY A K A
150
220
240 290
0
720
Kavsandorugu H.
240
200
220; 35 v
Dariyerihasanbey
275
310
31˚10'
350
150
143
300
2
200
4
Cinarli
70
175
M
6
Asagibakacak Mah.
115
U
O
U
15
N
8
275
40; 30 v
A
Kavakbiçki
T
400
I
4
130
10
N
Meselik T.
Amcahasanbey
Develibesni
330 380 335
Bayremzi
Cakirhaciibrahim
450 375 300
Site 1
310 325 Aydinpinar
Dip Mah.
km
Dereboyu Mah.
L
70
185
B O
Yenikoy
210 300 300 230 105 150 Bülbüldere Mah.
Saricökekköy
K AY N A S L I
290
340
230
Yörükler
280; 200 v
Cevizlik
300; 200 v
EFTEN LAKE
270; 350 v 250; 180-200 v 70 v
Celeköy
110
90 v
Hamamyani
80; 60 v
Liquefaction
Kurtballica
Cerkezballica
Surface rupture of 12 November 1999 Du¨zce earthquake. Numbers with arrow indicate lateral displacements; v, vertical
812
Güneyturbe H.
55 m-offset stream
450
12
22
Hataköy
Reworked part of August 1999 event Zekeriyaköy
Güven Sabakay H. 341 370 130 100 110 380 110 v
Cinardüzü
15
Cicubey 370
Mezarlik H.
Beyköy
31˚05'
150
853
Yanikkayak H.
9 199 ust, g u A
N
31˚00'
Surface Rupture and Slip Distribution of the 12 November 1999 Du¨zce Earthquake (M 7.1), North Anatolian Fault, Bolu, Turkey
southern strand goes into the Mudurnu valley, and the northern strand forms the Du¨zce–Hendek fault in the north surrounding a crustal block called the Almacık block. In the 17 August 1999 event (M 7.4) at least 140 km of the northernmost branch was ruptured between Karamu¨rsel and Go¨lyaka (Barka et al., 1999). In this article we present the rupture geometry and slip distribution along the rupture zone of the 12 November Du¨zce earthquake.
The Surface Rupture of the Du¨zce (M 7.1) Earthquake The Du¨zce earthquake formed a 40-km-long surface rupture zone. There is a 4-km releasing step-over at the eastern end of the August surface rupture around Eften Lake. The surface rupture began in the eastern end of the Karadere valley, 5 km west of the Eften Lake, with 10–50 cm dextral offset that was overlapped with the eastern end of the 17 August earthquake (Hartleb et al., 1999). The general trend
63
of the surface rupture of Du¨zce earthquake is almost east– west; however, it varies between N75⬚W and N75⬚E. The maximum vertical displacement along the southern margin of the Eften Lake was 350 cm, and an additional 300 cm of right-lateral offset was also measured (Figs. 2 and 3). Three liquefaction events were observed around Cevizlik and C¸ınarlı villages, diameters ranged between 0.7 and 12 m, and heights ranged from 8 to 50 cm (Fig. 2). The amount of right-lateral offset increases toward the central part of the rupture zone. A 450-cm offset is measured around the village of C¸ınarlı (Figs. 2, 4, and 5; site 1). The maximum offset is 500 Ⳳ 5 cm around Gu¨ven village (Figs. 2, 6, and 7; site 2). The offsets were clearly observed and measured on roads, fences, tree lines, rivers and streams, and buildings (Fig. 6). The trace of rupture was located in a narrow deformation zone changing between 0.5 and 50 m (mostly 2–5 m) in width. There were en-echelon tension cracks oriented between N50⬚W and N75⬚W in a relatively broader deformation zone. Two restraining step-over areas, 200 m in the east of Cicubey and 500 m around Gu¨rcu¨ler village, were mapped. In these areas, the connecting segments were made up of thrust and en-echelon thrust faults (Fig. 2). Toward the east, the rupture zone cuts the old main road, and the amount of displacement varies between 150 and 310 cm until Dereboyu village, located in the eastern part of Du¨zce–Kaynas¸lı plain (Fig. 2). In this area, surface rupture cuts the viaducts of the new highway, which is under construction, with 150-cm offset, causing extensive deformations on the legs of the viaduct. The amount of offset further diminishes to a few tens of centimeters or less on the
30
Figure 3.
Vertical displacement in the south of the
Eften Lake.
Distance NS (m)
20
10
0 4.5 ± 0.5m -10
-20
-30
-20
-10
0
10
Distance EW (m)
Figure 4.
Offset garden fences around C¸ınarlı village (450 cm).
Figure 5.
Survey with total station on garden fences around C¸ınarlı village (site 1, for location see Fig. 2).
20
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H. S. Akyu¨z, R. Hartleb, A. Barka, E. Altunel, G. Sunal, B. Meyer, and R. Armijo 20
a 10
NS distance (m)
0
-10
-20
-30
-40
-50 -50
Figure 6.
Maximum dextral offset site on Du¨zce earthquake surface rupture (Guven village road; 500 Ⳳ 5 cm).
-40
-30
-20
-10
0
10
20
EW distance (m)
20
b 10
Slip Distribution of the 12 November Du¨zce Earthquake The slip distribution of 12 November earthquake is shown in Figure 9. It appears that the average dextral offset is nearly 300 cm on a large part of the rupture. Maximum dextral slip is located on the central part of the rupture. The strike-slip displacement decreases sharply at both ends of the rupture. The western part of the rupture zone terminates at the Go¨lyaka pull-apart basin, where normal faulting is dominant. There are also some other vertical motions, normal faults, and thrust faults in the step-over areas along the Du¨zce rupture zone. These features are mostly shallow structures that occur in the upper part of the seismogenic zone. Even though a large normal component was observed in the teleseismic data, field observations indicated dominant strike slip and minor vertical motion along the main rupture zone.
Discussion and Conclusions Figure 8 shows the large earthquakes around Bolu that occurred in the twentieth century, including 17 August and 12 November earthquakes. The 1957, 1967, and the western end of the 1944 earthquakes occurred on the southern part of the Almacık block. The August event occurred in a partly northwestern margin of the Almacık block, the Karadere segment, extending as far as Go¨lyaka. This easternmost segment of the August event (Karadere segment) had a maxi-
0
-10
-20
y en m
offset 5 ± 0.5 m y en m
NS distance (m)
Bolu Mountain area to the eastern end of the rupture and disappears near the Bolu tunnel (Fig. 8). The trace of the rupture clearly follows the older fault morphology in some places. Two offset streams were measured as 55 m and 12 m around S¸ims¸ir and east of Gu¨ven, respectively, which confirms the previous earthquakes (Fig. 2).
-30
-40
-50 -50 -40 -40 -30 -30 -20 -20 -10 -10
0
0
10 10 20 20
Figure 7. Survey with total station on Gu¨ven village road (site 2, for location see Fig. 2). x en m
mum lateral offset of 150 cm (Hartleb et al., 1999), and it ended with a couple of centimeters in the southwestern part of Eften Lake with a releasing step-over north of Go¨lyaka (Fig. 2). The 12 November 1999 Du¨zce earthquake caused a motion that overlapped about 9 km with the August rupture, having a maximum dextral offset of 300 cm and vertical offset of 350 cm in the southwest part of Eften Lake. The November 1999 event caused rupture on the unbroken part of the fault mosaic surrounding the Almacık block three months after the August event. Considering the general westward migration of the North Anatolian fault since 1939, Barka (1996) predicted at least 1.5- to 2-m slip deficit in the west of Bolu, revealed from the comparison of the maximum slip that occurred during the 1944, 1957, and 1967 events; specifically, 3.5- to 4-m dextral slip was measured in the Bolu area resulting from the 1944 event, whereas the maximum slip in the Mudurnu valley changed between 1.6 and 2.6 m during the 1957 and 1967 events. However, the 5-m maximum slip is twice as high as the predicted slip along the 12 November rupture zone. This
Surface Rupture and Slip Distribution of the 12 November 1999 Du¨zce Earthquake (M 7.1), North Anatolian Fault, Bolu, Turkey
65
YIGILCA
Hasanlar Reservoir
Konuralp
CILIMLI
Tullukiris H.
(?) 1943
1657
CUMAOVA
DUZCE E5 Road
Ka radikmen H.
y hwa
TEM
1388
Hig
150-300
Hacisuleymanbey
ust Aug 99 9 1
Haciyakup
120-10
150-450
GOLYAKA Eften Lake
Beykoy
Guven Caykoy 10
50; 300 v
?
Kaynasli
Kavakbuku
Aydinpinar
Bolu Tunnel
200-500
Hamamustu
1577
Dariyeri Hasanbey
Mengencik
B O L U
1944
12 November 1999
1830
1729
1630
A L M A C I K
B L O C K
1967
1720
N Ab ant L ake
1957 1767
10 km
Akkavsak H. 1628
Figure 8. Active faults around Bolu. Numbers with arrow indicate lateral displacements; v, vertical separation.
600
Offset (cm)
500 400
300 200 100
0 0
5
10
15
20
Distance (km)
Figure 9.
25
30 dextral displacement
35
40
45
vertical separation
Slip distribution of the 12 November 1999 earthquake.
may suggest that the maximum slip along the 1944 was more than 4 m, perhaps as much as 6 m. An unbroken part of 10–12 km between the eastern end of the Du¨zce fault and Bolu may still exist, which may cause a M ⬍ 6.5 earthquake. The other possibility is that this might have already ruptured during the 1944 earthquake.
References Barka, A. (1996). Slip distribution along the North Anatolian Fault associated with large earthquakes of the period 1939–1967, Bull. Seism. Soc. Am. 59, 521–589. Barka, A. (1999). Marmara Denizi’nin Deprem Potansiyeli, Tu¨bitak Bilim ve Teknik 383, 28–32.
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H. S. Akyu¨z, R. Hartleb, A. Barka, E. Altunel, G. Sunal, B. Meyer, and R. Armijo
Barka, A., H. S. Akyu¨z, E. Altunel, G. Sunal, Z. Cakir, A. Dikbas, B. Yerli, T. Rockwell, J. Dolan, T. Dawson, R. Hartleb, A. Tucker, T. Fumal, R. Langridge, H. Stenner, S. Christofferson, R. Armijo, B. Meyer, and J. B. Chabalier (1999). 17 August 1999 I˙zmit Earthquake, Northwestern Turkey, EOS 80 (Suppl.), no. 46, F647. Hartleb, R., T. Dawson, A. Z. Tucker, J. Dolan, T. Rockwell, B. Yerli, A. Dikbas¸, Z. C¸akır, T. Gu¨rer, B. Uslu, and A. Barka (1999). Surface rupture and slip distribution along the Du¨zce strand of the 17 August 1999 ˙Izmit, Turkey Earthquake, EOS 80 (Suppl.), no. 46, F761. Hubert, A., A. Barka, E. Jacques, S. Nalbant, B. Meyer, R. Armijo, P. Tapponier, and J. King (2000). Seismic hazard in the Marmara Sea region following the 17 August 1999 I˙zmit earthquake, in 1999 I˙zmit ¨ . Kozacı, and Du¨zce Earthquakes: Preliminary Results, A. Barka, O ¨ Publication, ˙Istanbul TechH. S. Akyu¨z, and E. Altunel (Editors), ˙ITU nical University Press, ˙Istanbul, 311–316. Parsons, T., S. Toda, R. Stein, A. Barka, and J. Dieterich (2000). Heightened odds of large earthquakes near I˙stanbul: an interaction-based probability calculation, Science 288, no. 28, 661–665. I˙stanbul Technical University Department of Geology I˙stanbul, Turkey (H.S.A., G.S.)
University of Southern California Department of Earth Sciences Los Angeles, California (R.H.) ˙Istanbul Technical University Eurasia Institute of Earth Sciences ˙Istanbul, Turkey (A.B.)
Osmangazi University Department of Geology Eskisehir, Turkey (E.A.)
Institute Physique de Globe Paris, France (B.M., R.A.) Manuscript received 14 November 2000.
