Crustal Stress in the Northern Red Sea Region as Inferred from Seismic b-values, Seismic Moment Release, Focal Mechanisms, Gravity, Magnetic, and Heat Flow Data

Abstract

This study explores the spatial distribution of seismicity, the pattern of b-values, gravity and magnetic anomalies, heat flow data, and focal mechanism solutions to more thoroughly understand the present-day stress distribution and the nature of the crust, which characterize the rifting process in the northern Red Sea region. The region shows alternating low and high b-values in congruence with low and high cumulative seismic moment releases, respectively, and with negative and positive gravity anomalies, respectively. In general, except for larger-sized earthquake locations that characterized by high stress accumulation, low b-values, low seismic moment release, and low-gravity anomalies dominate the zones of the Gulf of Aqaba and the Gulf of Suez, thereby implying low stress accumulation consistent with an old crust of no differential development. Conversely, the rest of the Northern Red Sea region exhibited heterogeneities in the spatial distribution of b-values, cumulative seismic moment releases, and gravity anomalies, thereby implying stress heterogeneities. The stress heterogeneities may impute to the differences in material properties of the upper crust in the region. Zones of a positive Bouguer anomaly and high stress are notably associated with a relatively weak crust characterized by high rate of seismicity, while zones of the negative Bouguer anomaly and low stress characterized an older and more stable crust. However, details on the nature of crust required additional geophysical and geological data of high resolution in future studies.