# Seismic and Geodetic Crustal Moment-Rates Comparison: New Insights on the Seismic Hazard of Egypt
## 9 Seismic-Geodetic Moment-Rates Ratio
Four delimited seismic sources are characterized by lower SCC values (less than 20%). They are the EG-05, EG-06, EG-08, and EG-10 seismic sources. They cover the seismicity along the central Red Sea region, the triple junction between the Gulf of Suez, Gulf of Aquaba, and the Red Sea, the northern Nile Delta block, and the central part of the Nile Valley, respectively (Figure 8). Such a result suggests that in these sectors, deformation occurs prevailingly in an aseismic mode. As mentioned above, moment-rates estimations for EG-08 and EG-10 must be considered with caution, being the computed strain-rates not homogeneously distributed within the seismic zones. Since the moment-rates estimations have been performed by taking into account the largest strain-rate values for both zones, we performed an additional computation by considering the average strain-rate value. Achieved results do not significantly alter the previous considerations, being the new SCC values increasing of a factor of 1.3 and 2.2 for the EG-08 and EG-10 zones, respectively. Another ratio range is observed for the sources EG-01, EG-04, EG-07, and EG-09 (Figure 8), characterized by moderate SCC values (between 20% and 60%). They defined the seismic activity along the southern Gulf of Aquaba, northeastern Sinai and eastern Mediterranean coast, the southern and central parts of the Gulf of Suez, and the Cairo-Suez district and northern Gulf of Suez, respectively (Figure 8). Therefore, these moderate SCC values are suggesting that these areas account for only an intermediate seismic fraction from the total budget of the deformation rate. Some of these seismic regions are characterized by well-known active faults that frequently generate moderate seismic activity such as in the Cairo-Suez district, the southern and central half-gra  
Figure 8: Seismic coupling coefficient (SCC) is depicted as percentage of the seismic-geodetic moment-rate ratio. Finally, the highest SCC values (actually >100%, labeled as >60% in Figure 8) have been reached in the current study for the EG-02 and EG-03 seismic sources. Both zones are located along the GoA-DST which extends in the NE-SW direction. Such results suggest that the crustal deformation is mostly released through seismic activity. As mentioned above, strain-rate estimation for EG-03 concentrated only on the western side of the source, while no estimations are available for the eastern side. The high SCC value (Table 3) in this source points to an underestimation of the geodetic rates or an overestimation of the seismic ones, as discussed previously. The high seismic rate is well constrained because of the long-time interval covered by the catalog as well as the occurrence of some M \(\geq\) 6.0 earthquakes (since 590 A.D.). Moreover, an underestimation of geodetic rates could be possible because of the existence of very few stations within the seismic zone, which therefore would not be enough to properly constrain the deformation pattern of active faults. Regarding the EG-02 source, seismic moment-rate, as explained previously, was computed from individually recorded earthquakes in the last 50 years. This implies that the obtained result must be also considered with care.