Preprints
https://doi.org/10.5194/nhess-2021-323
https://doi.org/10.5194/nhess-2021-323

  22 Nov 2021

22 Nov 2021

Review status: this preprint is currently under review for the journal NHESS.

Slow build-up of turbidity currents triggered by a moderate earthquake in the Sea of Marmara

Pierre Henry1, Sinan Özeren2, Nurettin Yakupoğlu3, Ziyadin Çakir3, Emmanuel de Saint-Léger4, Olivier Desprez de Gésincourt4, Anders Tengberg5, Cristele Chevalier6, Christos Papoutsellis1, Nazmi Postacıoğlu7, Uğur Dogan8, Hayrullah Karabulut9, Gülsen Uçarkuş3, and M. Namık Çağatay3 Pierre Henry et al.
  • 1Aix Marseille Univ, CNRS, IRD, INRAE, Coll France, CEREGE, Aix-en-Provence, France
  • 2Istanbul Technical University, Eurasia Institute of Earth Sciences, Maslak, Istanbul, Turkey
  • 3Istanbul Technical University, Geological Engineering Dept., Maslak, Istanbul, Turkey
  • 4CNRS, DT INSU, Parc national d’instrumentation océanographique, Plouzané, France
  • 5Aanderaa Data Instruments AS, Bergen, Norway
  • 6Aix Marseille Univ, CNRS, IRD, MIO, Aix-en-Provence, France
  • 7Istanbul Technical University, Physics Dept., Maslak, Istanbul, Turkey
  • 8Yıldız Technical University, Geomatic Engineering Dept., Istanbul, Turkey
  • 9Bogazici University, KOERI, Istanbul, Turkey

Abstract. Earthquake-induced submarine slope destabilization is known to cause debris flows and turbidity currents, but the hydrodynamic processes associated with these events remain poorly understood. Records are scarce and this notably limits our ability to interpret marine paleoseismological sedimentary records. An instrumented frame comprising a pressure recorder and a Doppler recording current meter deployed at the seafloor in the Sea of Marmara Central Basin recorded consequences of a MW = 5.8 earthquake occurring Sept 26, 2019 and of a Mw = 4.7 foreshock two days before. The smaller event caused sediment resuspension but no strong current. The larger event triggered a complex response involving a mud flow and turbidity currents with variable velocities and orientations, which may result from multiple slope failures. A long delay of 10 hours is observed between the earthquake and the passing of the strongest turbidity current. The distance travelled by the sediment particles during the event is estimated to several kilometres, which could account for a local deposit on a sediment fan at the outlet of a canyon, but not for the covering of the whole basin floor. We show that after a moderate earthquake, delayed turbidity current initiation may occur, possibly by ignition of a cloud of resuspended sediment. Some caution is thus required when tying seismoturbidites with earthquakes of historical importance. However, the horizontal extent of the deposits should remain indicative of the size of the earthquake.

Pierre Henry et al.

Status: open (until 03 Jan 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on nhess-2021-323', Anonymous Referee #1, 26 Nov 2021 reply
  • RC2: 'Comment on nhess-2021-323', Anonymous Referee #2, 29 Nov 2021 reply
    • CC1: 'Reply on RC2', Pierre Henry, 29 Nov 2021 reply

Pierre Henry et al.

Data sets

EMSO / MAREGAMI Marmara bottom pressure and current records Henry Pierre, Özeren Sinan, Desprez De Gesincourt Olivier, de Saint-Leger Emmanuel, Libes Maurice, Çakir Ziyadin, Yakupoğlu Nurettin, Geli Louis https://doi.org/10.17882/78928

MARNAUT (CTD data - vertical profiles) HENRY Pierre , SENGOR Celal , CAGATAY Namik https://doi.org/10.17600/7010070

Pierre Henry et al.

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Short summary
Seafloor instruments at the bottom of the Sea or Marmara recorded disturbances caused by earthquakes, adressing the minimum magnitude that may be recorded in the sediment. A magnitude 4.7 caused turbidity but little current. A magnitude 5.8 earthquake caused a mud flow and strong currents that spread sediment on the seafloor over several kilometers. However, most of known earthquake deposits in the Sea of Marmara spread over larger zones and should correspond to larger earthquakes.
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