Estimation of successive coseismic vertical offsets using coeval sedimentary events – application to the southwestern limit of the Sea of Marmara's Central Basin (North Anatolian Fault)

Abstract

Abstract. In the deep part of the Sea of Marmara (Turkey), the sedimentation developing upon the North Anatolian Fault is strongly influenced by the associated seismic activity, through gravity reworking (fluidized landslides) and tsunamis. Specific layers (homogenites + turbidites, HmTu), representing individual sedimentary events, have been characterized along three giant piston cores retrieved from the Çinarcik and Central (or Orta) basins. Pre-Holocene, nonmarine sediments, were analyzed, representing the last 12-17 kyr BP (before present). For a 2 kyr long interval, 11 events could be precisely correlated on both sides of the Central Basin's southwestern scarp. For each of them, based on the specific depositional process, the thickness difference between the two sites was considered as a direct estimation of the vertical component of a coeval coseismic offset. The homogenite (upper) component accounts for the major part of the thickness difference (ranging from 36 to 144 cm). These offsets were considered as likely representing dominantly vertical throws, along the transtensional southwestern boundary of the inner, pull-apart Central Basin. In terms of natural hazards, further investigations on this local behavior should rather be directed to tsunami genesis.

A review of 20 years (1999–2019) of Turkish–French collaboration in marine geoscience research in the Sea of Marmara

“…The sedimentological study of the 2001 MARMACORE cruise giant piston cores revealed that a considerable part of the sedimentary succession in the deep Marmara basins consists of turbidites, most of which were likely triggered by earthquakes. Radiocarbon dating of the cores indicated high sedimentation rates (1-3 m/ka) in the deep Marmara basins, which could allow the individual seismic events to be distinguished in the sedimentary succession (e.g., Beck et al 2007Beck et al , 2015Eriş et al 2012). Moreover, Beck et al (2007) also discovered a 5-8-m thick, 16-ka-old turbidite-homogenite (T-H) unit of tsunamogenic origin in cores MD01-2431 and MD01-2429 in the Central Basin.…”

“…This information is in turn important for probabilistic earthquake risk assessment. Such studies in the Sea of Marmara started after the 1999 İzmit earthquake (Polonia et al 2002;2004;McHugh et al 2006), but increased considerably after Turkish-French geoscience collaboration, with the recovery of long piston cores and seafloor observations using ROV Victor and manned submersible Nautile (Armijo et al 2005;Beck et al 2007Beck et al , 2015Drab 2012;Çağatay et al 2012;Eris et al 2012;McHugh et al 2014). Up to 38 m-long cores allowed to obtain earthquake records extending back to several thousands of years, and to match the more recent ones with the 2500-yearlong historical records of the Marmara Region (Ambraseys and Finkel 1995;Ambraseys 2002;Guidoboni et al 1994;Gui-doboni and Comastri 2005).…”

Multi‐scale and multi‐parametric analysis of Late Quaternary event deposits within the active Corinth Rift (Greece)

“…These elements have been analysed, event‐by‐event, for sedimentary records (either marine or lacustrine) that span as much as tens of thousands of years (Marco & Agnon, 1995; Rodriguez‐Pascua et al ., 2000), with correlations established between several different sites (McHugh et al ., 2006; Goldfinger et al ., 2007; Gràcia et al ., 2010; Polonia et al ., 2013, 2017; Ratzov et al ., 2015). Establishing relationships between element (3) and the two other elements, requires precise knowledge of a fault system’s activity, and of the sedimentary fill adjacent to the fault (McHugh et al ., 2014; Beck et al ., 2012, 2015; Vanneste et al ., 2018; Van Daele et al ., 2019).…”

Active Subaquatic Fault Segments in Lake Iznik Along the Middle Strand of the North Anatolian Fault, NW Turkey

“…Compared to historical and terrestrial archives, lake sediments provide a complementary and more continuous paleoseismic record (e.g., Strasser et al, 2013; Wilhelm et al, 2016). Combining on‐fault studies such as trenching with studies investigating earthquake‐induced turbidites in lakes not only provides direct evidence for fault displacement in the case of surface ruptures (e.g., Beck et al, 2015) but also allows to document seismic events off‐fault without surface ruptures (Brocard et al, 2016). We propose here to investigate Lake Iznik using a combined geophysical and sedimentological approach to provide new insights into the seismicity of the Iznik region over the past millennia.…”