No. 1p. 339-3512001 Paleoseismic investigation of the 1999 Duzce earthquake fault at Lake Efteni, North Anatolian fault system, Turkey 1 2 2 Omer Emre 3 Ahamet Dogan 3 Selim Ozalp 3 4 4 4 1 Toshihiko Sugai 1, Yasuo Awata 2, Shinji Toda 2, Omer Emre 3, Ahamet Dogan 3, Selim Ozalp 3 Tsuyoshi Haraguchi 4, Hirohisa Kinoshita 4, Keita Takada 4 and Masaaki Yamaguchi 1 Abstract: In order to reveal the recurrence and displacement of past faultings on the 1999 Duzce earthquake (M7.1) segment, we investigated subsurface geology across the 1999 earthquake rupture which appeared along the southern side of the Lake Efteni. We used a 6-m-long, 50-cm-wide, and 10-cm-thick geoslicer to sample sediments in tectonically subsided area at intervals of 5-10 m. The sediments are divided into 6 units based on angular unconformities. The second oldest unit 2, mainly composed of mudflow deposits, drops toward the north more than 15 m. The unit 2 is covered by younger fine sediments with several angular unconformities probably associated with surface faultings. Two probable and two possible faulting events are identified after the deposition of unit 2. From the radiocarbon dates (about 2 ka) of the peat layer just above unit 2, the average recurrence interval of faultings is calculated around 400 to 500 years and the vertical displacement of each individual faulting is estimated at 2.5 to 3 m. Moreover, we can point out the possibility that the penultimate faulting event occurred later than A.D. 1650. The Duzce fault shows very high activity during the past 2000 years. Key words: North Anatolian fault, 1999 Duzce earthquake fault, Lake Efteni, geoslicer NAF193967 M 6 1 Ambraseys, 1970Stein et al., 1997 1999 8 17 Izmit M7.4 120 km 1 Awata et al., 2000 11 12 Duzce M7.1 8 40 km Emre et al., 2000 1999 11 NAF 11 Bolu Sapanca NAF 1999 11 NAF 2000 1999 11 Sugai et al., 2000 2001a, b 14 C 1 University of Tokyo 2 Active Fault Research Center 3 Mineral Research and Exploration of Turkey 4 Fukken Co., Ltd. 9 7 925-1 -
1999 11 Elmacik 2 1 11 5.3 m 2 3 m3 m 2Emre et al., 2000 3 11 4 55 m 2.5 m 1999 11 6 m 50 cm 10 10 515 m 6 cm 5 3 5 3 14 C 67 1 3 5 8 unit 16 unit unit 1 GS-7 GS-10 unit 1 14 C 29,090 36,960 1 unit 2 67 unit 36 unit 3 Br.1 Br. 2 unit 3 13 m 8 Br.1, 2, 3, 4, GS-5 14 C 2 1 2BR10.07 5GS5.40 unit 3/4 Br.1 Br.2 unit 3 GS-5 4 m colluvial wedge unit 2 unit 3/4 GS-5 2.5 m 9 GS-5 GS-5 GS-6 GS-10 GS-5 GS-1 GS-4 Br.13 unit 4 unit 5 unit 4/5 (9 Br.1, GS-3, 4, 5, 6) unit 5 unit 4 GS- GS-7 unit 5 unit 6 250 14 C 1 3GS1.30 17 GS-4 GS-5 unit 5/6 GS-5 GS-5-2 -
unit 2 2 unit 5/6 unit 4/5 2 unit 4 unit 3/4 8 Unit 5/6 unit 4/5 unit 4 unit 3/4 unit 3 unit 3 Br.3 Br.4 6 m 89 unit 4/5 Br.3 Br.4 1.52 m 44.5 m unit 3unit 4 2 Br.1 Br.2 unit 3/4 GS-6 2 m unit 2 unit 5 1999 11 unit 5/6 unit 6 unit 5/6 14 C 1 3GS1.3, 5GS0.95, 5GS1.15, 6GS1.00 unit 5/6 4 GS-5 GS-5 14 C 10 1999 11 1650 2 400500 unit 3 15 m 5 GS-7 unit 2 unit 2 GS-5 unit 3 unit 3 2 2 15 m 7.5 mm/ 1999 11 10 mm/ 2 56 1 3.34 m 2.53 m 1999 11 3.34 m 20 NAF Stein et al., 1997 1999 11 unit 16 4-3 -
14 C 2 400500 1999 1650 1 2.53m 3.34m 2 1999 11 Ahrmet Dogan Ambraseys, N.N. (1970) Some characteristic features of the North Anatolian fault zone. Tectonophysics, 9, 143-165. Awata, Y., Yoshioka, T., Emre, O., Duman, T.Y., Dogan, A. and Tsukuda, E. (2000) Segment structures of the surface ruptures associated with the August 17, 1999 Izmit earthquake, Turkey. Book of Abst. Papers, XXVII General Assem. Euro. Seismol. Commis., 149-153. Emre, O., Duman, T.Y., Awata, Y., Dogan, A. and Ozalp, S. (2000) Surface ruptures of November 12 1999 Duzce earthquake, NW Turkey. Book of Abst. Papers, XXVII General Assem. Euro. Seismol. Commis., 247-252. Stein, R. S., Barka, A.A and Dietrich, H.J. (1997) Progressive failure on the North Anatolian fault since 1939 by earthquake stress triggering. Geophys. J. Int., 128, 594-604. Sugai, T., Toda, S., Takada, K., Emre, O., Awata, Y., Dogan, A., Haraguchi, T., Kinoshita, H. Tokay, F. and Duman, T.Y. (2000) Evidence for the repetitive coseismic subsidence of the Lake Eften along the Duzce segment, North Anatolian fault, Turkey. EOS, F816 (Abstracts for the AGU 2000 Fall meeting). 2000 1999 11 2000 P087 2001a 1999 11 no. 60 Omer Emre 2001b 1999 11 no. 20, 104-111. - 4 -
北アナトリア断層系 1999 年デュズジェ地震断層の古地震調査 5
須貝俊彦 粟田泰夫 遠田晋次 Omer Emre Tamer Y. Duman 原口強 木下博久 高田圭太 山口正秋 6
北アナトリア断層系 1999 年デュズジェ地震断層の古地震調査 7
須貝俊彦 粟田泰夫 遠田晋次 Omer Emre Tamer Y. Duman 原口強 木下博久 高田圭太 山口正秋 8
北アナトリア断層系 1999 年デュズジェ地震断層の古地震調査 9
須貝俊彦 粟田泰夫 遠田晋次 Omer Emre Tamer Y. Duman 原口強 木下博久 高田圭太 山口正秋 10
北アナトリア断層系 1999 年デュズジェ地震断層の古地震調査 11
須貝俊彦 粟田泰夫 遠田晋次 Omer Emre Tamer Y. Duman 原口強 木下博久 高田圭太 山口正秋 Table 1. Results of the radiocarbon dating. Location of each sample is shown in Fig. 9. 12
1 Photo 1 (top). Distant view of the survey site on the south of Lake Efteni. 2 1999 Photo 2 (middle). The 1999 Nov. 16th earthquake rupture near the survey site. 3 GS-1GS-10 Photo 3 (bottom). Geoslicer samples, GS-1 to GS-10, laid on the survey site for observation. - 13 -