Active fault segments along the North Anatolian Fault system in the Sea of Marmara: implication for seismic hazard

Type Article
Acceptance Date 2021 IN PRESS
Language English
Author(s) Gasperini LucaORCID1, Stucchi Massimiliano2, Cedro Vincenzo1, Meghraoui Mustapha3, Ucarkus Gulsen4, Polonia Alina1
Affiliation(s) 1 : Istituto Di Scienze Marine, Consiglio Nazionale Delle Ricerche (ISMAR-CNR), Bologna, Italy
2 : Istituto Nazionale Di Geofisica E Vulcanologia, Bologna, Italy
3 : Université de Strasbourg, Strasbourg, France
4 : Geological Engineering Department, Istanbul Technical University, Istanbul, Turkey
Source Mediterranean Geoscience Reviews (2661-863X) (Springer Science and Business Media LLC) In Press
DOI 10.1007/s42990-021-00048-7
Keyword(s) North Anatolian fault, Sea of Marmara, Earthquakes, Active fault segments, Marine geophysics, Seismic hazard
Abstract

A new analysis of high-resolution multibeam and seismic reflection data, collected during several oceanographic expeditions starting from 1999, allowed us to compile an updated morphotectonic map of the North Anatolian Fault below the Sea of Marmara. We reconstructed kinematics and geometries of individual fault segments, active at the time scale of 10 ka, an interval which includes several earthquake cycles, taking as stratigraphic marker the base of the latest marine transgression. Given the high deformation rates relative to sediment supply, most active tectonic structures have a morphological expression at the seafloor, even in presence of composite fault geometries and/or overprinting due to mass-wasting or turbidite deposits. In the frame of the right-lateral strike-slip domain characterizing the North Anatolian fault system, three types of deformation are observed: almost pure strike-slip faults, oriented mainly E–W; NE/SW-aligned axes of transpressive structures; NW/SE-oriented trans-tensional depressions. Fault segmentation occurs at different scales, but main segments develop along three major right-lateral oversteps, which delimit main fault branches, from east to west: (i) the transtensive Cinarcik segment; (ii) the Central (East and West) segments; and (iii) the westernmost Tekirdag segment. A quantitative morphometric analysis of the shallow deformation patterns observed by seafloor morphology maps and high-resolution seismic reflection profiles along the entire basin allowed to determine nature and cumulative lengths of individual fault segments. These data were used as inputs for empirical relationships, to estimate maximum expected Moment Magnitudes, obtaining values in the range of 6.8–7.4 for the Central, and 6.9–7.1 for the Cinarcik and Tekirdag segments, respectively. We discuss these findings considering analyses of historical catalogues and available paleoseismological studies for the Sea of Marmara region to formulate reliable seismic hazard scenarios.

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