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Variability of the stress pattern in the continental margin of Egypt
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  • Asem Mostafa Taha Mohamed Salama,
  • Mohamed Nabil ElGabry,
  • Hesham Hussein,
  • Mona Abdelazim
Asem Mostafa Taha Mohamed Salama
National Research Institute of Astronomy and Geophysics
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Mohamed Nabil ElGabry
National Research Institute of Astronomy and Geophysics

Corresponding Author:[email protected]

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Hesham Hussein
National Research Institute of Astronomy and Geophysics
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Mona Abdelazim
National Research Institute of Astronomy and Geophysics
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Abstract

We have studied the focal mechanisms of eleven earthquakes with magnitudes of ML ≥ 3.8 on the continental margin of Egypt and the adjacent onshore region from 1951 to 2020 to identify the stress regime and its spatial variations. The uncertainty parameters of each solution are evaluated using HASH software. The stress pattern obtained from focal solutions in the western province matches a compressional stress field with an NNW-SSE orientated compression axis, which corresponds to the direction of movement of the Nubia plate relative to Eurasia. On the other hand, the stress pattern derived from drilling-induced fractures and borehole breakout measurements is not correlated with the identified stress axis. The focal solutions of the recent earthquakes in the eastern-central province of the Nile Deep-Sea Fan indicate the strike-slip stress regime is the prevailing mode of deformation with an almost horizontal ESE-WSW compression axis and an almost horizontal N-S extension axis. Two responsive conjugate strike-slip faults that include both sinistral and dextral faults accommodate this strike-slip deformation style. The stress regime existing in the eastern-central province directly contradicts the northward convergent of the Nubian-Anatolia plates along the Cypriot arc. The stress pattern deflection in the eastern-central province of the Nile Deep-Sea Fan may be attributed to kinematic adaptation resulting from the deformation in and around the Eratosthenes Seamount rigid block as it impinges on the central part of the Cypriot arc. Toward the Egyptian onshore, the extension pattern was behaving differently from the compression stress pattern of the offshore continental margin.