THE NORTH ANATOLIAN FAULT: Anewlook

18 Mar 2005 19:32 AR AR233-EA33-02.tex AR233-EA33-02.sgm LaTeX2e(2002/01/18) P1: IKH 10.1146/annurev.earth.32.101802.120415 Annu. Rev. Earth Planet. Sci. 2005. 33:37–112 doi: 10.1146/annurev.earth.32.101802.120415 Copyright c 2005 by Annual Reviews. All rights reserved First published online as a Review in Advance on July 16, 2004 THE NORTH ANATOLIAN FAULT: ANewLook A.M.C. S¸engor,¨ 1,3 Okan Tuys¨ uz,¨ 1,3 Caner Imren,˙ 2 Mehmet Sakınç,1 Haluk Eyidogan,˘ 2 Naci Gor¨ ur,¨ 1,3 Xavier Le Pichon,4 and Claude Rangin4 1Istanbul˙ Teknik Universitesi,¨ Avrasya Yer Bilimleri Enstitus¨ u,¨ Ayazaga˘ 34469, Istanbul,˙ Turkey; email: [email protected], [email protected], [email protected], [email protected] 2Istanbul˙ Teknik Universitesi,¨ Maden Fakultesi,¨ Jeofizik Bol¨ um¨ u,¨ Ayazaga˘ 34469, Istanbul,˙ Turkey; email: [email protected], [email protected] 3Istanbul˙ Teknik Universitesi,¨ Maden Fakultesi,¨ Jeoloji Bol¨ um¨ u,¨ Ayazaga˘ 34469, Istanbul,˙ Turkey 4College` de France—Chaire de Geodynamique,´ Europoleˆ de l’Arbois, Batiment Laennec,¨ hall D, etage´ 2 BP 80—13545 Aix-en-Provence, France; email: [email protected], [email protected] KeyWords strike-slip faulting, shear zone development, earthquake faulting, the Sea of Marmara, tectonics of Turkey Dedicated to the memory of three pioneers, Ihsan˙ Ketin, Sırrı Erinç and Melih Tokay, and a recent student, Aykut Barka, who burnt himself out in pursuit of the mysteries of the North Anatolian Fault. ■ Abstract The North Anatolian Fault (NAF) is a 1200-km-long dextral strike-slip fault zone that formed by progressive strain localization in a generally westerly widen- ing right-lateral keirogen in northern Turkey mostly along an interface juxtaposing subduction-accretion material to its south and older and stiffer continental basements to its north. The NAF formed approximately 13 to 11 Ma ago in the east and propagated westward. It reached the Sea of Marmara no earlier than 200 ka ago, although shear- by California Institute of Technology on 01/09/13. For personal use only. related deformation in a broad zone there had already commenced in the late Miocene. The fault zone has a very distinct morphological expression and is seismically active. Annu. Rev. Earth Planet. Sci. 2005.33:37-112. Downloaded from www.annualreviews.org Since the seventeenth century, it has shown cyclical seismic behavior, with century- long cycles beginning in the east and progressing westward. For earlier times, the record is less clear but does indicate a lively seismicity. The twentieth century record has been successfully interpreted in terms of a Coulomb failure model, whereby every earthquake concentrates the shear stress at the western tips of the broken segments leading to westward migration of large earthquakes. The August 17 and November 12, 1999, events have loaded the Marmara segment of the fault, mapped since the 1999 earthquakes, and a major, M ≤ 7.6 event is expected in the next half century with an approximately 50% probability on this segment. Currently, the strain in the Sea of Marmara region is highly asymmetric, with greater strain to the south of the Northern Strand. This is conditioned by the geology, and it is believed that this is generally the case for the entire North Anatolian Fault Zone. What is now needed is a more detailed 0084-6597/05/0519-0037$20.00 37 18 Mar 2005 19:32 AR AR233-EA33-02.tex AR233-EA33-02.sgm LaTeX2e(2002/01/18) P1: IKH 38 S¸ENGOR¨ ET AL. geological mapping base with detailed paleontology and magnetic stratigraphy in the shear-related basins and more paleomagnetic observations to establish shear-related rotations. INTRODUCTION The North Anatolian Fault (NAF) [Figures 1 (see color insert) and 2] is one of the largest currently active strike-slip faults in the world, forming the most prominent part of a medium-size strike-slip-dominated belt of deformation, i.e., a keirogen (Ketin 1948, S¸engör 1979a; for keirogen, see S¸engör & Natal’in 1996, p. 639, note 8), in northern Turkey. It extends from the Gulf of Saros in the northern Aegean Sea to the town of Karlıova (39◦18N, 41◦01E) in Eastern Turkey for 1200 km, paralleling roughly the southern Black Sea shores and keeping a fairly regular distance of some 100 km to the coast, connecting the Aegean taphrogen (Taymaz et al. 1991, Ozeren¨ 2002, Yilmaz et al. 2002) with the East Anatolian high plateau (S¸aro˘glu 1985, Ko¸cyi˘git et al. 2001, S¸engör et al. 2003). The dextral shear asso- ciated with the NAF continues across the northern Aegean, crosses northern and central mainland Greece as a broad shear zone (termed the Grecian Shear Zone by S¸engör 1979a), and eventually links up with the Hellenic subduction zone (Dewey & S¸engör 1979, McKenzie and Jackson 1983, Le Pichon et al. 1993). Although the NAF has been subject to numerous geological, geomorphological, and geophysical (especially seismological) investigations since its recognition as a major strike-slip fault in 1948 by Ihsan˙ Ketin (Ketin 1948; see previous reviews and syntheses by Ketin 1957, 1969, 1976; Pavoni 1961; Allen 1969, 1982; Ambraseys 1969; S¸engör 1979a; Barka 1981, 1992; S¸engör & Canıtez 1982; S¸engör et al. 1982; Kiratzi 1993; also see the following symposium: Anonymous 1973), national and international interest concerning the fault has literally exploded since the catastrophic earthquakes of August 17, 1999 [Barka 1999; Barka et al. 2000a, 2002; see especially the richly documented bilingual book by Emre et al. (2003)], and November 12, 1999 (Akyüz et al. 2000, 2002). Since then, a vast by California Institute of Technology on 01/09/13. For personal use only. amount of geological, geophysical, and geotechnical data have been gathered in the Sea of Marmara [where the probability of rupture by a large earthquake within Annu. Rev. Earth Planet. Sci. 2005.33:37-112. Downloaded from www.annualreviews.org the next 50 years is high (Parsons et al. 2000, King et al. 2001, Atakan et al. 2002; also see Figure 13 (see color insert) last frame] and around it (Karaca & Ural 1999, Barka et al. 2000b, Do˘gan & Kurter 2000, Yaud et al. 2000, Ansal 2001, Taymaz 2001, Aksu & Yaltırak 2002, Görür et al. 2002, Toksöz 2002, Altunel & Akyüz 2003, Anonymous 2003a; also see the Rangin et al. 2001 atlas and Görür 2002, 2003), filling a previously existing gap in our knowledge of the course and character of the NAF in its western part because of its submarine location. The amount, diver- sity, quality, and the density of data collected in a few years are unparalleled in the history of geological investigations in Turkey and do not have many counterparts in the world. This great acceleration of activity in and around the Sea of Marmara also has triggered other studies along the fault. Many old problems have been looked at 18 Mar 2005 19:32 AR AR233-EA33-02.tex AR233-EA33-02.sgm LaTeX2e(2002/01/18) by California Institute of Technology on 01/09/13. For personal use only. Annu. Rev. Earth Planet. Sci. 2005.33:37-112. Downloaded from www.annualreviews.org THE NORTH ANATOLIAN FAULT Figure 2 The North Anatolian Keirogen (NAK). All the faults shown in this map have formed in relation to the NAK. Not all of them are now active, but all have been active sometime in the past 11 Ma. Most are potential earthquake generators. Fault traces delineated by heavier lines represent the most active parts of the keirogen constituting the structure known as the North Anatolian Fault (NAF). Note that the keirogen is entirely confined to the area underlain by Tethyside accretionary complexes (see also Figure 4). The faults have been compiled chiefly from Tüysüz (1985), S¸aro˘glu et al. (1987, 1992), Bingöl (1989), Eyido˘gan (1991), Barka (1993), Dirik (1993), Yilmaz et al. (1997a), Akyüz et al. (2000), Barka et al. (2000a, b), Herece & Akay (2003), S¸enel (2002), and our own observations. For the sources concerning the Tethyside accretionary complexes, see Figure 4. P1: IKH 39 18 Mar 2005 19:32 AR AR233-EA33-02.tex AR233-EA33-02.sgm LaTeX2e(2002/01/18) P1: IKH 40 S¸ENGOR¨ ET AL. from different viewpoints using different methods and new technologies (the results of these new studies have been reported, in addition to scattered papers in international literature, some of which are cited below, in the following workshop reports: Tatar et al. 2000, Altunel et al. 2001, Anonymous 2001, 2003b, Gökten et al. 2001, Emre et al. 2002; also see the following compendium: Altunel & Akyüz 2003). Unlike previous catastrophic earthquakes in Turkey, the location of the August 17 and November 12, 1999, events in a densely populated region of the country, where much of the Turkish industry is located, has led to unprecedented public interest in the NAF (e.g., Ç orlu 1999; also see Atakan et al. 2002). The fact that the city of Istanbul˙ (population ≈15 million), an international center of trade and culture from time immemorial, is now under serious large earthquake threat in the foreseeable future (e.g., Durukal et al. 2002, Erdik et al. 2003) has added an earnest international dimension to the public interest (e.g., Deli & Pérouse 1999, Pérouse 2001). New ideas on the trigger function of big earthquakes for other large shocks in large regions widened the international scientific and public interest (e.g., Papadopoulos 2002). All of this international scientific activity and public con- cern inevitably generated a vast and multifarious literature in a very short time.

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