# Seismic and Geodetic Crustal Moment-Rates Comparison: New Insights on the Seismic Hazard of Egypt
## 10 Summary and Conclusions  
Although the comparison between the seismic and geodetic moment-rates implies several assumptions and approximations, it provides important insights into the seismic hazard of potential active tectonic regions. Despite the different approaches operated by several authors for different studied regions worldwide, their estimations and comparisons enabled the achievement of valuable results which sometimes document the agreements between geodetic and seismic moment-rates, and other times the larger values of the geodetic moment-rates against the seismic ones. In the current work, an updated and Poissonian earthquake catalog (2200 B.C.-2020 A.D.) for Egypt, focal mechanism solutions (1951-2019) coming from previous publications, and the original GNSS data were used to study the spatial and temporal seismic and geodetic moment patterns. An attempt has been made to compare the seismic and geodetic moment-rates in order to provide a statistical estimation for the deformation budget in the surroundings of Egypt and therefore to give more insights into the seismic hazard of the studied region. Considering the geological and tectonic settings of the studied region as well as the previously mentioned data (seismicity, focal mechanisms, and GNSS data), ten broad shallow crustal seismic sources (EG-01 to EG-10; h \(<\) 35 km) have been delimited. These zones mainly cover the potential shallow active seismic regions along the GoA-DST, the Gulf of Suez-Red Sea Rift, and the Nile River and its delta. The lack of GPS data in other regions (e.g., Aswan region, northwestern coast, and the Western Desert of Egypt) prevent us from estimating the geodetic moment-rate, hence no further seismic sources were defined for these regions. The different seismicity parameters (average annual activity rate, maximum observed magnitude, seismogenic depth, \(b\)-value, and maximum expected magnitude) were estimated for the proposed sources both for the Gutenberg-Richter and the characteristic earthquake models, when necessary, taking into account the completeness period for each magnitude range. The seismic and geodetic moment-rates have been computed, using the previously mentioned algorithms, for the delimited seismic sources. The estimation of such rates was challenging for several reasons. The heterogeneous coverage of the GNSS data in some regions (e.g., strain-rate estimation for EG-03, EG-08, and EG-10 sources), the incompleteness of the earthquake sub-catalog (e.g., unexpected high \(b\)-values for EG-02 and EG-05 zones), and the own computation of seismic moment-rate for some sources (EG-02 and EG-10) were the most difficult problems in this work. Keeping in mind these considerations, geodetic and seismic moment-rates for some sources should be considered with caution. Based on the computed seismic-geodetic moment-rate ratio (seismic coupling coefficient \"SCC\") for the studied sources, three main categories were differentiated according to their seismic behavior in and around Egypt. The first region/category comprises a large sector of the delimited sources: the Red Sea, the Gulf of Aqaba, the Nile Delta, and the Nile Valley (EG-05, EG-06, EG-08, and EG-10 sources). They are characterized by low SCC values (<20%), evidencing the aseismic deformation behavior. The second region, characterized by moderate SCC values (between 20% and 60%), comprises the southern Gulf of Aqaba, northeastern Sinai and the Eastern Mediterranean coast, the Gulf of Suez, and the Cairo-Suez district (EG-01, EG-04, EG-07, and EG-09 sources). Such moderate SCC values confirm that the crustal earthquake activity for this region accounts only for a moderate fraction of the total budget of deformation. Finally, the third region that has higher SCC values extends along the GoA-DST (EG-02 and EG-03 sources). These values highlight a fully seismic deformation behavior in this region.