Source characteristics of the 16 June 2020 ML 5.4 earthquake and its significant aftershock sequences, northern Red Sea, Egypt

Abstract

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 omega^{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.