Submarine fault scarps in the Sea of Marmara pull-apart (North Anatolian Fault): Implications for seismic hazard in Istanbul Rolando Armijo, Nicolas Pondard, Bertrand Meyer, Gulsen Uçarkus, Bernard Mercier de Lépinay, Jacques Malavieille, Stéphane Dominguez, Marc-André Gutscher, Sabine Schmidt, Christian Beck, et al. To cite this version: Rolando Armijo, Nicolas Pondard, Bertrand Meyer, Gulsen Uçarkus, Bernard Mercier de Lépinay, et al.. Submarine fault scarps in the Sea of Marmara pull-apart (North Anatolian Fault): Implications for seismic hazard in Istanbul. Geochemistry, Geophysics, Geosystems, AGU and the Geochemical Society, 2005, 6, pp.Q06009. 10.1029/2004GC000896. hal-00112155 HAL Id: hal-00112155 https://hal.archives-ouvertes.fr/hal-00112155 Submitted on 15 Feb 2011 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Article Geochemistry 3 Volume 6, Number 6 Geophysics 24 June 2005 Q06009, doi:10.1029/2004GC000896 GeosystemsG G ISSN: 1525-2027 AN ELECTRONIC JOURNAL OF THE EARTH SCIENCES Published by AGU and the Geochemical Society Submarine fault scarps in the Sea of Marmara pull-apart (North Anatolian Fault): Implications for seismic hazard in Istanbul Rolando Armijo, Nicolas Pondard, Bertrand Meyer, and Gulsen Uc¸arkus Laboratoire de Tectonique, UMR 7578, CNRS, IPGP, 4 Place Jussieu, F-75252 Paris Cedex 05, France ([email protected]) Bernard Mercier de Le´pinay Geosciences-Azur, UMR 6526, CNRS Universite´ Nice Sophia-Antipolis, Valbonne, France Jacques Malavieille and Ste´phane Dominguez Laboratoire de Dynamique de la Lithosphe`re, UMR 5573, CNRS, Universite´ Montpellier 2, Montpellier, France Marc-Andre´ Gustcher IUEM Domaines Oce´aniques, UMR 6538, CNRS, Universite´ de Bretagne Occidental, Plouzane´, France Sabine Schmidt EPOC, UMR 5805, CNRS, Universite´ Bordeaux 1, Talence, France Christian Beck Laboratoire de Ge´odynamique des Chaıˆnes Alpines, UMR 5025, CNRS, Universite´ de Savoie, Le Bourget du Lac, France Namik C¸ agatay, Ziyadin C¸ akir, Caner Imren, Kadir Eris, and Boris Natalin Mining Faculty, General Geology Department, Istanbul Technical University (ITU), Maslak Istanbul, Turkey Serdar O¨ zalaybey and Leyla Tolun Scientific and Technical Research Council of Turkey (TUBITAK) Marmara Research Center (MAM), Earth and Marine Sciences Research Institute, Kocaeli, Turkey Ire`ne Lefe`vre UMR 1572, CNRS, Laboratoire des Sciences du Climat et de l’Environnement, Gif-sur-Yvette, France Leonardo Seeber Lamont-Doherty Earth Observatory, Palisades, New York 10964, USA Luca Gasperini Istituto di Geologia Marina CNR-ISMAR, I-40129 Bologna, Italy Claude Rangin UMR 6535, CNRS, Colle`ge de France, CEREGE, Aix-en-Provence, France Omer Emre and Kerim Sarikavak Geological Research Department, General Directorate of Mineral Research and Exploration (MTA), Balgat Ankara, 06520, Turkey Copyright 2005 by the American Geophysical Union 1 of 29 Geochemistry 3 armijo et al.: sea of marmara pull-apart Geophysics 10.1029/2004GC000896 Geosystems G [1] Earthquake scarps associated with recent historical events have been found on the floor of the Sea of Marmara, along the North Anatolian Fault (NAF). The MARMARASCARPS cruise using an unmanned submersible (ROV) provides direct observations to study the fine-scale morphology and geology of those scarps, their distribution, and geometry. The observations are consistent with the diversity of fault mechanisms and the fault segmentation within the north Marmara extensional step-over, between the strike-slip Ganos and Izmit faults. Smaller strike-slip segments and pull-apart basins alternate within the main step-over, commonly combining strike-slip and extension. Rapid sedimentation rates of 1–3 mm/yr appear to compete with normal faulting components of up to 6 mm/yr at the pull-apart margins. In spite of the fast sedimentation rates the submarine scarps are preserved and accumulate relief. Sets of youthful earthquake scarps extend offshore from the Ganos and Izmit faults on land into the Sea of Marmara. Our observations suggest that they correspond to the submarine ruptures of the 1999 Izmit (Mw 7.4) and the 1912 Ganos (Ms 7.4) earthquakes. While the 1999 rupture ends at the immediate eastern entrance of the extensional Cinarcik Basin, the 1912 rupture appears to have crossed the Ganos restraining bend into the Sea of Marmara floor for 60 km with a right-lateral slip of 5 m, ending in the Central Basin step-over. From the Gulf of Saros to Marmara the total 1912 rupture length is probably about 140 km, not 50 km as previously thought. The direct observations of submarine scarps in Marmara are critical to defining barriers that have arrested past earthquakes as well as defining a possible segmentation of the contemporary state of loading. Incorporating the submarine scarp evidence modifies substantially our understanding of the current state of loading along the NAF next to Istanbul. Coulomb stress modeling shows a zone of maximum loading with at least 4–5 m of slip deficit encompassing the strike-slip segment 70 km long between the Cinarcik and Central Basins. That segment alone would be capable of generating a large- magnitude earthquake (Mw 7.2). Other segments in Marmara appear less loaded. Components: 15,506 words, 12 figures, 1 video. Keywords: continental deformation; earthquake scarps; Istanbul; Marmara; seismic hazard; submarine morphology. Index Terms: 7223 Seismology: Earthquake interaction, forecasting, and prediction (1217, 1242); 7230 Seismology: Seismicity and tectonics (1207, 1217, 1240, 1242); 8110 Tectonophysics: Continental tectonics: general (0905) Received 13 December 2004; Revised 2 March 2005; Accepted 24 March 2005; Published 24 June 2005. Armijo, R., et al. (2005), Submarine fault scarps in the Sea of Marmara pull-apart (North Anatolian Fault): Implications for seismic hazard in Istanbul, Geochem. Geophys. Geosyst., 6, Q06009, doi:10.1029/2004GC000896. 1. Introduction westward appears as a major transtensional step- over of the NAF dominated by pull-apart tectonics [2] The North Anatolian Fault (NAF) has almost and slip partitioning at a range of scales [Armijo et entirely ruptured during a series of large destruc- al., 1999, 2002; Flerit et al., 2003] (Figure 1). It is tive earthquakes in the past century. The sequence thus probable that crustal scale extensional strains propagated 800 km westward between 1939 and and significant normal faulting add complexity to 1999; an observation that has stimulated funda- earthquake generation in the Marmara region. The mental studies of fault interaction mechanics, stress study of the geomorphology of active faults on transfer and earthquake rupture processes [Toksoz land appears worldwide as a good approach to et al., 1979; Stein et al., 1997; Nalbant et al., 1998; unravel fault bends, slip partitioning and possible Hubert-Ferrari et al., 2000; Parsons et al., 2000]. mechanical interactions between fault segments. Assessment of seismic hazard in the city of Istan- Methods in tectonic morphology have greatly ad- bul, which is located near the western tip of the vanced over the last 25 years aided by satellite propagating sequence, is no independent issue. A imagery, digital topography and modern techniques uniform right-lateral strike-slip motion parallel to for dating, which allow quantitative measures [e.g., the Anatolia/Eurasia plate boundary may have Wallace, 1981; Hanks et al., 1984; Armijo et al., facilitated the westward progression of earthquake 1986, 1989; Peltzer et al., 1988; Avouac et ruptures along most of the eastern and central NAF. al., 1993; Wesnousky and Jones, 1994; Meyer et However, the Sea of Marmara region located al., 1998; Hubert-Ferrari et al., 2002; Van der 2of29 Geochemistry 3 armijo et al.: sea of marmara pull-apart Geophysics 10.1029/2004GC000896 Geosystems G Figure 1 3of29 Geochemistry 3 armijo et al.: sea of marmara pull-apart Geophysics 10.1029/2004GC000896 Geosystems G Woerd et al., 2002a; Ritz et al., 2003; Me´riaux et concentrate most of the plate motion [Straub et al., al., 2004]. Here we adapt a similar approach for the 1997; Armijo et al., 1999; McClusky et al., 2000; submarine faults. The MARMARASCARPS cruise Flerit et al., 2003]. The North Marmara basin is performed in 2002 collected high-resolution data located by the conspicuous 70-km-wide step-over to characterize the submarine morphology. These between two strike-slip faults, well-known on land, include microbathymetry, photo/video imagery which have ruptured with purely right-lateral mo- andsedimentsamplingacquiredwithaROV tion during recent earthquakes, both with similar (Remotely Operated Vehicle), as well as coring magnitude (M 7.4) and clear surface rupture. One and 3.5 kHz profiling with systematic coverage of is the 1912 Ganos earthquake that ruptured the the most prominent fault scarps in the northern Sea Dardanelles region to the west of the Marmara Sea; of Marmara. Together with data collected on other the second is the Izmit earthquake that ruptured recent cruises we examine the morphology of in 1999 east of the Marmara Sea (Figure