# Seismic and Geodetic Crustal Moment-Rates Comparison: New Insights on the Seismic Hazard of Egypt
## 6 Delimitation of Seismic Sources
### Seismic Sources along the Gulf of Suez-Red Sea Rift (EG-05 to EG-07)  
The Gulf of Suez-Red Sea (GoS-RS) NW-trending rift (Figure 1) extends from the Gulf of Aden (to the south) to the tip of the Gulf of Suez (to the north), for about 1900 km between the uplifted shoulders of the Nubian and Arabian plates. The GoS-RS region could be subdivided into four main zones, based on its morphology and structure, which reflects specific stages in the creation of the spreading center [76]. They are the southern Red Sea \"active sea-floor spreading\", central Red Sea \"transition zone\", northern Red Sea \"late-stage continental rifting\", and the active rifting zones. The first zone is located between 15\({}^{\circ}\) and 20\({}^{\circ}\) N latitudes and is characterized by a well-developed axial trough developed through the normal seafloor spreading during the last 5 Ma [77] or at about 9-12 Ma [78]. The second zone is situated between 20\({}^{\circ}\) to about 23\({}^{\circ}\)20\({}^{\prime}\) N latitudes, in which the axial trough of the rift becomes discontinuous and consists of a series of \"deeps\" alternating with shallow \"inter-troughs\" [79]. The third zone represents the northern Red Sea (Figure 1). However, there are small isolated \"deeps/depressions\", which consist of a broad trough without a clear spreading center [76]. The last zone, that both could be added to the first one or could be considered as a separate one, is the future line along which the southern Red Sea is going to propagate through the Danakil Depression Afar (to the south). To the north, the Gulf of Suez (Figure 1b) acts as the NW-trending divergent plate boundary between the Nubian plate (to the west) and the Sinai sub-plate (to the east) [80]. Together with the Gulf of Aqaba and the Red Sea, it acts as one of the three arms of the Sinai triple junction [31; 63; 81] (see Figure 1). The Gulf of Suez was interpreted by several researchers [82; 83] to be composed of three half-grabens separated by two accommodation zones: Gharandal and Morgan accommodation zones [84] (see Figure 1b). Both accommodation zones show discrete normal, oblique, and strike-slip faults [85]. In the current work, the following seismic sources were delimited along the GoS-RS rift. Seismic source EG-05 (Figures 3-5) covers the seismic activity concentrating on the central Red Sea zone, as well as the dispersed seismicity on the Red Sea western coast and the Abu Dabbab region, in the Eastern Desert of Egypt. This zone is characterized by a relatively moderate seismic activity in comparison with the zones at the surroundings of the Sinai Peninsula (along the two arms of both gulfs). Only three slightly damaging historical earthquakes are reported to be located within this delimited source. They are the 997, 1887, and 1899 earthquakes (Figure 3). The largest observed magnitude within this seismic source is the 12 November 1955 (mb 6.2, Mw 5.7) earthquake (Figure 4). The few available focal mechanisms are characterized by prevailing normal-faulting features (Figure 5). EG-06 covers the seismicity on the triple junction between the Red Sea, the Gulf of Aqaba, and the Gulf of Suez (Figures 3-5). This source is characterized by relatively higher seismicity than the previous one, which is mainly related to the juncture between these two gulfs [23; 86]. No historical earthquakes have been reported within this source (Figure 3), while the recent 16 June 2020 (Mw 5.5) earthquake represents the maximum recorded magnitude (Figure 4, Table 1). Available focal mechanisms reflect both strike-slip and normal-faulting features (Figure 5). The first mechanism category may relate to earthquakes that originated along the transform faults crossing the main rift (Figure 1b), while the second one is related to those earthquakes that originated along the main rift itself [87; 88]. EG-07 covers the seismic activity of the southern and central parts of the Gulf of Suez (Figures 3-5) and represents the northward prolongation of the previous source.