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.