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Submarine Earthquake History of the Çınarcık Segment of the North

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Submarine Earthquake History of the Çınarcık Segment of the North Submarine Earthquake History of the Çınarcık Segment of the North Anatolian Fault in the Marmara Sea, Turkey Laureen Drab, Aurélia Hubert-Ferrari, Sabine Schmidt, Philippe Martinez, Julie Carlut, Meriam El Ouahabi To cite this version: Laureen Drab, Aurélia Hubert-Ferrari, Sabine Schmidt, Philippe Martinez, Julie Carlut, et al.. Sub- marine Earthquake History of the Çınarcık Segment of the North Anatolian Fault in the Marmara Sea, Turkey. Bulletin of the Seismological Society of America, Seismological Society of America, 2015, 105 (2A), pp.622-645. 10.1785/0120130083. insu-01571132 HAL Id: insu-01571132 https://hal-insu.archives-ouvertes.fr/insu-01571132 Submitted on 1 Aug 2017 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. Bulletin of the Seismological Society of America, Vol. 105, No. 2A, pp. 622–645, April 2015, doi: 10.1785/0120130083 Submarine Earthquake History of the Çınarcık Segment of the North Anatolian Fault in the Marmara Sea, Turkey by Laureen Drab,* Aurélia Hubert-Ferrari, Sabine Schmidt, Philippe Martinez, Julie Carlut, and Meriam El Ouahabi Abstract The North Anatolian fault (NAF) in the Marmara Sea is a significant haz- ard for the city of Istanbul. The use of paleoseismological data to provide an accurate seismic risk assessment for the area is constrained by the fact that the NAF system is submarine; thus a history of paleoearthquakes can be inferred only by using marine sediment cores. Here, a record of turbidites was obtained in two cores and used to reconstruct the earthquake history along the Çınarcık segment, a main branch of the NAF. Klg04 was collected from a berm north of the fault, and Klg03 was positioned in the Çınarcık basin, south of the fault. The cores were correlated using long-term geo- chemical variations in the sediment, and turbidites deposited simultaneously at both sites were then identified. Radionuclide measurements suggest the most recent turbi- M dite was triggered by the 1894 C.E. w 7.3 earthquake. We conclude that the turbidites identified at both sites are earthquake generated, based on their particular sedimento- logical and geochemical signatures; the correlation of turbidites at berm and basin sites; and the match of the most recent turbidite with a nineteenth century historical earthquake. To date older turbidites, we used carbon-14 and paleomagnetic data to build an OxCal model with a local reservoir correction of 400 50 yr. The Çınarcık segment is found to have ruptured in 1509 C.E., sometime in the fourteenth century, in 989 C.E., and in 740 C.E., with a mean recurrence interval in the range of 256–321 years. Finally, we used the earthquake record obtained to review the rupture history of the adjacent segments over the past 1500 years. Introduction M >7 Constraining the recurrence rate of w earthquakes generally been identified based on their synchronicity at dif- that threaten the megacity of Istanbul is problematic because ferent sites and their distinctive sedimentological or geo- the late Holocene faults are submarine. Istanbul, with 12 mil- chemical signatures (Gorsline et al., 2000; Nakajima and lion inhabitants, borders the Marmara Sea (Fig. 1a), a sub- Kanai, 2000; Shiki et al., 2000; Beck et al., 2007; Masson marine pull-apart basin related to the North Anatolian fault et al., 2011; Drab et al., 2012). In the case of the Marmara (NAF), a major strike-slip fault that ruptures in large magni- Sea, several studies (McHugh et al., 2006; Sarı and Çağatay, M tude earthquakes. Since the 1999 w 7.4 Izmit earthquake, 2006; Beck et al., 2007; Drab et al., 2012) revealed that its stresses have further increased in the eastern part of the Mar- sediments contain a record of turbidites triggered by large mara Sea (Hubert-Ferrari et al., 2000; Parsons et al., 2000; earthquakes. These turbidites have been used to constrain Pondard et al., 2007). Understanding past ruptures of the the history of earthquakes rupturing across a given depocen- NAF in the Marmara Sea is thus a key issue in assessing seis- ter (McHugh et al., 2006; Drab et al., 2012). The present mic hazards for this area. study shows that marine sediment cores can be used to con- Subaqueous paleoseismology can reconstruct the his- strain paleoruptures of the NAF segment located just south of tory of large earthquakes on submarine faults (Goldfinger, Istanbul and to evaluate the recurrence rate of large magni- 2011), as shaking associated with large offshore earthquakes tude earthquakes in this area. triggers submarine landslides and turbidity currents. The re- Here, we apply subaqueous paleoseismology to two sulting deposits can be sampled by sediment coring, charac- gravity cores located in the Çınarcık basin of the Marmara terized, and dated. Earthquake-generated turbidites have Sea (Fig. 1b). The Çınarcık basin is located ∼20 km to the south of Istanbul and is north bounded by the Çınarcık fault, *Now at Lamont Doherty Earth Observatory, Columbia University, 61 the main segment of the NAF. In the two cores, we identified Route 9W Palisades, New York 10964; [email protected]. and characterized turbidite deposits using their grain size and 622 Submarine Earthquake History of the Çınarcık Segment of the NAF in the Marmara Sea, Turkey 623 Figure 1. (a) Global geodynamic context of the Anatolian plate with Global Positioning System velocities from Reilinger et al. (2006). The location of the Marmara Sea (shown in [b]) is indicated with a box. (b) General tectonic map of the Marmara Sea, crossed by the North Anatolian fault (NAF). Basins, highs, and main segments of the fault are indicated from the west to the east with different lines, and their names are given in the gray box to the right. The study area (shown in [c]) is depicted with a box. Historical earthquakes located by Am- braseys (2002) are represented with rupture dates and dots. (c) The map of Çınarcık basin. Location of the two studied cores is represented with respect to the Çınarcık fault segment. Arrows show sediment paths for turbidite deposits (Altınok et al., 2011). The line crossing the two cores represents the topographic profile presented in (d). White crosses represent the location of other published cores discussed in the study. (d) Topographic profile of the northern part of the Çınarcık basin. The profile starts close to the center of the Çınarcık basin. The color version of this figure is available only in the electronic edition. geochemical characteristics. We also used east Mediterra- gering mechanisms of the turbidites. Radiogenic lead (210Pb) nean-scale changes in sedimentation to correlate the two and cesium (137Cs) data allowed us to date and correlated the records to a reference core located in a nonturbidite deposi- turbidites at the top of the sediment columns with recent his- tional environment. We then investigated the possible trig- torical earthquakes. Radiocarbon dating (14C) combined 624 L. Drab, A. Hubert-Ferrari, S. Schmidt, P. Martinez, J. Carlut, and M. El Ouahabi with paleomagnetic data enabled us to construct an age seismicity during the end of the thirteenth and fourteenth model for the core Klg04 located in a berm in the Çınarcık centuries in the Marmara area (Ambraseys and Finkel, 1991). fault scarp (Fig. 1c,d) and to date turbidites over the last 1500 The 989 C.E. earthquake principally affected the Istanbul years. Finally, the NAF rupture behavior in the Marmara Sea region, with a tsunami reaching the city (Ambraseys and Fin- is discussed. kel, 1991; Altınok et al., 2011). Historical data predomi- nantly locate the event in the Çınarcık basin (Ambraseys, 2002; Guidoboni and Comastri, 2005). Finally, the 740 M Setting w 7.1 C.E. earthquake was associated with a large tsunami (Altınok et al., 2011). It has been generally located in the Tectonic and Paleoseismological Background Çınarcık basin (Ambraseys, 2002; Guidoboni and Comastri, The NAF is a major dextral strike-slip fault extending 2005), but some authors suggested an epicenter location in over 1200 km in northern Turkey and in the Aegean Sea the Izmit Gulf or Central basin (McHugh et al., 2006; Ber- (Barka and Kadinsky-Cade, 1988; Sengör et al., 2005) trand et al., 2011; Çağatay et al., 2012). Historical informa- (Fig. 1a). In the Marmara Sea, the NAF accommodates a dex- tion for older ages is limited, but Ambraseys (2002) located tral horizontal motion of 18:5 mm=yr (Kurt et al., 2013) the 407 C.E. and 437 C.E. earthquakes in the Çınarcık basin. spread over a width of 130 km (Barka and Kadinsky-Cade, Based only on historical reports, it is difficult to unam- 1988). Most of the deformation is localized on the northern biguously associate an offshore earthquake with a given sub- branch of the NAF (Armijo et al., 2002), which crosses the marine fault (Table 1). Even studies combining historical Marmara Sea. The Marmara Sea is 170 km long, has a maxi- data with attenuation models (Parsons, 2004) or distribution mum water depth of 1250 m, and is composed of three aligned of slip deficit and Coulomb stress interaction (Pondard et al., pull-apart basins separated by two topographic ridges (Le 2007) propose different rupture scenarios across the Marmara Pichon et al., 2001; Armijo et al., 2002; Sarı and Çağatay, Sea. Subaqueous paleoseismological studies provide addi- 2006; Fig.
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