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Segmentation and Holocene Behavior of the Middle Strand of the North Anatolian Fault (NW Turkey)
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  • Yacine Benjelloun,
  • Julia De Sigoyer,
  • Stéphane Garambois,
  • Julien Carcaillet,
  • Yann Klinger
Yacine Benjelloun
Université de Paris

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Julia De Sigoyer
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Stéphane Garambois
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Julien Carcaillet
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Yann Klinger
Université de Paris, Institut de physique du globe de Paris, CNRS
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The North Anatolian fault in the Marmara region is composed of three parallel strands all separated by ~50 km. The activity of the middle strand, which borders the southern edge of the Marmara Sea, is much debated because of its present-day very low seismicity. The weak seismic activity observed today along the middle strand contrasts with historical, archaeological and paleoseismological evidence, which suggest several destructive earthquakes have occurred during the last 2000 years. Our study aims to better constrain seismic hazard on the middle strand by exploring its Holocene paleoseismicity. For this, we mapped 148 km of the middle strand, using high-resolution satellite imagery. A series of landforms offset by the middle strand activity have been systematically measured to recover the past ruptures. Three Late Pleistocene-Holocene terraces have been dated with the terrestrial cosmogenic nuclide method, constraining a horizontal slip rate of ~4.3 mm/yr. The statistical analysis of the offsets evidences several major ruptures preserved in the landscape, with coseismic lateral displacements ranging between 3 and 6.5 m. This corresponds to Mw ~7.3 earthquakes able to propagate along several fault segments. As the approach used can only resolve large magnitude events, smaller events (e.g. Mw 6.8-7) likely occurred as well even if their geomorphological signature could not be detected. Historical seismicity and paleoseismology data suggest that the last large earthquakes along the MNAF happened in 1065 CE and between the 14th and 18th centuries CE. Since then, the MNAF may have accumulated enough stress to generate a destructive rupture.
Nov 2021Published in Tectonics volume 40 issue 11. 10.1029/2021TC006870