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The northern Red Sea in eastern Egypt is one of the world's newest marine basins. The northern Red Sea is a very active seismic region and poses a significant hazard to the nearest cities on the Red Sea coast. On June 16, 2020, a moderate earthquake (ML = 5.4), as published by the Egyptian National Seismic Network (ENSN), occurred in the northern Red Sea followed by several aftershocks, ranging in magnitude from 2.0 to 3.4. The best-fitting double-couple movement obtained using the full waveform moment tensor inversion of the main earthquake indicated strike-slip movement, with a minor normal component. The two nodal main shock planes were oriented NNE–SSW and ESE–WNW, respectively. The aftershocks sequences distribution did not coincide with the 16 Jun, 2020 main earthquake, neither in map view nor with respect to depth which may pointed to a secondary fault plane activation and stress triggered by the mainshock. The aftershocks clustered at the north western side of the main earthquakes and extend in the north western direction, which supported that the ESE–WNW plane is the fault plane. The spectral parameters of the S-wave displacement spectra of the main earthquake and its significant aftershock sequences were determined using the spectral inversion method and Brune's ω 2 modulation. The obtained spectra are flat in the frequency range from 0.8 Hz to each corner frequency, and they decreased rapidly at frequencies of < 10 Hz. The calculated seismic moment, moment magnitude, corner frequency, source radius, and stress drop vary from 8.293E+18 to 7.541E+22 dyn·cm, 2.4 to 5.0, 2.2 to 8.2 Hz, 171 to 633 m, and 0.02 to 13 MPa, respectively. The moment magnitude is equal to or slightly higher than the local magnitude reported by ENSN. The calculated stress drops for the earthquakes increased with increasing earthquake size. [ABSTRACT FROM AUTHOR]

To determine whether recent seismicity around the High Dam Lake (Lake Nasser) in the Aswan region is induced or triggered by the lake reservoir or is of natural origin, we analyzed moment tensor solutions and source spectra of recent recorded earthquakes in the area. The earthquakes' focal mechanisms, including source mechanism parameters and source spectra, can give important information to assist in discriminating between triggered and natural seismic events. In the current work, we computed moment tensors and stress drop values for six recently triggered earthquakes recorded by the Egyptian National Seismic Network (ENSN) around Lake Nasser, Aswan area, with local magnitudes between 3.0 and 4.6, as well as 40 nearby earthquakes in and around Egypt with local magnitudes ranging from 4.0 to 5.5, that are known as natural events. We performed full waveform inversion for the studied seismic events, including the dominant double-couple (DC) signature, and also completed moment tensor solutions. Our results show that most triggered events demonstrated significant non-double-couple components. The focal depths of most Aswan seismic events calculated in the current study are significantly shallower than the estimated focal depths for inter-plate and intraplate earthquakes in and around the area under investigation. The focal depths of 80% of the triggered events are shallower than 10 km, while 80% of the tectonic earthquakes are deeper than 15 km. On the other hand, stress and source spectra of the studied events are used as another key to deeply study the source mechanics and physics of natural and triggered events in this area. [ABSTRACT FROM AUTHOR]