# Seismic and Geodetic Crustal Moment-Rates Comparison: New Insights on the Seismic Hazard of Egypt
## 9 Seismic-Geodetic Moment-Rates Ratio  
The seismic-geodetic moment-rate ratios (in percentages) for the proposed seismic sources in Egypt are referred to herein as the \"seismic coupling coefficient; SCC\" [6; 12]. The seismic moment-rate is a measure of the elastic unloading rate, and the geodetic moment-rate is a measure for both elastic and anelastic loading rates [6]. The resulting ratio between the seismic and geodetic moment-rates (SCC) theoretically ranges between 0 and 100%. Closer percentages to 100% reflect that a large amount of the deformation budget was released by earthquakes, however, lower percentages suggest either accumulating strain not released by earthquakes or a significant proportion of aseismic deformation [6]. The SCC exceeds the 100% value when seismic moment-rate values are greater than the geodetic ones, and is usually observed in areas where the seismic catalogs cover a relatively short time and contain large earthquakes [12]. \begin{table}
\begin{tabular}{l c c c c c c c c c c c} \hline
**Source** & **n (Mw \(\geq\) 4.0)** & **m\({}_{\text{max}}\) obs.** & **Date** & **D50** & **D90** & \(\Lambda\) (\(\geq\)4.00) & **b-Value** & **\(\Delta\)m ** & 40.6-1.6 & 6.25 \(\pm\) 0.56 & 213.0 \\ EG-03 & 96 & 34 & Mw 7.7 & 746\(-\)/ & 11.0 & 22.5 & 1.04 \(\pm\) 0.11 & 0.85 \(\pm\) 0.02 & 35.7-7 & 7.85 \(\pm\) 0.56 & 69.2 \\ EG-04 & 54 & 34 & Mw 7.7 & 748\(-\)/ & 9.9 & 20.3 & 0.47 \(\pm\) 0.06 & 0.81 \(\pm\) 0.04 & 35.7-7 & 7.85 \(\pm\) 0.40 & 40.0 \\ EG-05 & 37 & Mb 6.2, Mw 5.7 & 1995/(11/22) & 12.0 & 23.0 & 2.09 \(\pm\) 0.36 & 1.35 \(\pm\) 0.11 [FOOTNOTE:]Footnote 1: Magnitude interval for which the Gutenberg-Richter relationship was fitted.[ENDFOOTNOTE] & 40.5-7.5 & 5.85 \(\pm\) 0.40 & 5.7 \\ EG-06 & 44 & Mw 5.5 & 2020/(06/16) & 10.9 & 23.8 & 1.53 \(\pm\) 0.20 & 1.25 \(\pm\) 0.19 & 35.5-5.5 & 5.80 \(\pm\) 0.07 & 3.1 \\ EG-07 & 68 & Mw 6.8, MS 6.6 & 1969/(03/31) & 14.4 & 25.0 & 1.49 \(\pm\) 0.20 & 0.98 \(\pm\) 0.04 & 40.6-8 & 7.15 \(\pm\) 0.26 & 19.5 \\ EG-08 & 34 & mb 6.5, Mw 6.4 & 1955/(09/12) & 20.0 & 27.0 & 0.29 \(\pm\) 0.05 & 0.92 \(\pm\) 0.05 & 35.4-6.4 & 6.50 \(\pm\) 0.39 & 2.1 \\ EG-09 & 97 & lX 3.4, Mw 6.7 & 1262/- & 9.6 & 25.0 & 1.14 \(\pm\) 0.13 & 1.65 \(\pm\) 0.04 & 40.6-7 & 6.75 \(\pm\) 0.54 & 7.4 \\ EG-10 & 27 & VIII, Mw 6.2 & 857/04\(-\) & 12.0 & 25.0 & 0.70 \(\pm\) 0.14 & 1.05 \(\pm\) 0.13 & 35.5-5.4 & 5.40 \(\pm\) 0.54 & 2.2 \\ \hline \end{tabular}
\end{table} 
Table 2: Number of earthquakes (Mw \(\geq\) 4.0), maximum recorded/observed magnitudes, D50 and D90 depth values, activity rates (\(\geq\)MW 4.0), and b-values of the Gutenberg–Richter relationship, maximum expected magnitudes (\(m_{\text{max}}\)), and the estimated seismic moment-rates for the proposed seismic sources. See the text for more explanation. Figure 6: Geodetic strain-rate field (after [61]) overlain by the defined seismic sources. Color scale range (from blue to red) in the background of the plot shows the areal change in the strain-rate field, while the arrows refer to the maximum extensional (in red) and maximum contractional (in blue) horizontal strain-rates.