EGU2020-3556, updated on 09 Jan 2024
https://doi.org/10.5194/egusphere-egu2020-3556
EGU General Assembly 2020
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Analysis of the foreshock sequences preceding two moderate (Mw4.7 and Mw5.8) earthquakes in the Sea of Marmara offshore Istanbul, Turkey.

Virginie Durand1, Stephan Bentz1, Grzegorz Kwiatek1,2, Georg Dresen1,3, Christopher Wollin1, Oliver Heidbach1, Patricia Martinez-Garzon1, Fabrice Cotton1,3, Murat Nurlu4, and Marco Bohnhoff1,2
Virginie Durand et al.
  • 1GFZ, Geomechanics and scientific drilling, POTSDAM, Germany (vdurand@gfz-potsdam.de)
  • 2Institute of Geological Sciences, Free University of Berlin, Berlin, Germany
  • 3University of Potsdam, Department of Geophysics, Potsdam, Germany
  • 4AFAD, Disaster and Emergency Management Presidency, Ankara, Turkey

In September 2019 a sequence of two moderate earthquakes (Mw4.7 and Mw5.8) occurred in the central Sea of Marmara (Turkey), SW of Istanbul. These events took place ate the transition between a creeping and a locked segment of the North Anatolian Fault. To investigate in detail the spatiotemporal evolution of the seismicity, we apply a matched-filter technique to continuous waveforms, thus reducing the magnitude threshold for detection. Sequences of foreshocks preceding the two mainshocks are clearly seen, exhibiting different behaviors: a migration of the seismicity along the entire fault segment on the long-term (several days before the mainshocks) and a concentration around the epicenters of the large events on the short-term (during the few hours preceding the mainshocks). We infer that both seismic and aseismic slip during the foreshock sequences change the stress state on the fault, bringing it closer to failure. Our observations also suggest that the Mw 4.7 event contributed to weaken the fault as part of the preparation process of the Mw 5.8 earthquake.

How to cite: Durand, V., Bentz, S., Kwiatek, G., Dresen, G., Wollin, C., Heidbach, O., Martinez-Garzon, P., Cotton, F., Nurlu, M., and Bohnhoff, M.: Analysis of the foreshock sequences preceding two moderate (Mw4.7 and Mw5.8) earthquakes in the Sea of Marmara offshore Istanbul, Turkey., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3556, https://doi.org/10.5194/egusphere-egu2020-3556, 2020.

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