Lithospheric strength variations and seismotectonic segmentation below the Sea of Marmara

The Sea of Marmara is a tectonically active basin that straddles the North Anatolian Fault Zone (NAFZ), a major strike-slip fault that separates the Eurasian and Anatolian tectonic plates. The Main Marmara Fault (MMF), which is part of the NAFZ, contains an approximately 150 km long seismotectonic s...

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Veröffentlicht in:Tectonophysics 2021-09, Vol.815, p.228999, Article 228999
Hauptverfasser: Gholamrezaie, Ershad, Scheck-Wenderoth, Magdalena, Cacace, Mauro, Bott, Judith, Heidbach, Oliver, Bohnhoff, Marco, Strecker, Manfred R.
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Sprache:eng
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Zusammenfassung:The Sea of Marmara is a tectonically active basin that straddles the North Anatolian Fault Zone (NAFZ), a major strike-slip fault that separates the Eurasian and Anatolian tectonic plates. The Main Marmara Fault (MMF), which is part of the NAFZ, contains an approximately 150 km long seismotectonic segment that has not ruptured since 1766. A key question for seismic hazard and risk assessment is whether or not the next rupture along this segment is likely to produce one major earthquake or a series of smaller earthquakes. Geomechanical characteristics such as along-strike variations in rock strength may provide an important control on seismotectonic segmentation. We find that variations in lithospheric strength throughout the Marmara region control the mechanical segmentation of the MMF and help explain its long-term seismotectonic segmentation. In particular, a strong crust that is mechanically coupled to the upper mantle spatially correlates with aseismic patches, where the MMF bends and changes its strike in response to the presence of high-density lower crustal bodies. Between the bends, mechanically weaker crustal domains that are decoupled from the mantle indicate a predominance of creeping. These results are highly relevant for the ongoing debate regarding the characteristics of the Marmara seismic gap, especially in view of the seismic hazard (Mw > 7) in the densely populated Marmara region. •3-D thermal and rheological models indicate lithospheric strength variations below the Sea of Marmara.•Due to a heterogeneous crustal configuration, rheological heterogeneities occur along the Main Marmara Fault (MMF).•Modeled rheological heterogeneities are consistent with the hypothesis that the MMF is mechanically segmented.•The seismogenic segmentation along the MMF is primarily controlled by a mechanically heterogeneous crust.
ISSN:0040-1951
1879-3266
1879-3266
DOI:10.1016/j.tecto.2021.228999