Three-dimensional structure of Conrad and Moho discontinuities in Egypt

Abstract

The three-dimensional structures of Conrad and Moho discontinuities beneath Egypt are investigated by local earthquake travel time inversion. A number of 2513 events with 24,696 arrival time data recorded by the Egyptian National Seismic Network (ENSN) are used. The station corrections of P- and S-waves and the hypocentral parameters are simultaneously estimated with the Conrad and Moho depths. The results of this study show that the discontinuities form patterns of shallow and deep structures getting shallow toward the northern and eastern coast, and deeper toward western Desert and northeastern Sinai. The Conrad and Moho discontinuities are located within the depth range 9–17km and 27–41km, respectively. The depth ranges of Conrad and Moho discontinuities are respectively: 15–16km and 31–33km in greater Cairo and Dahshour; 15–18km and 32–35km in Sinai; 16–17 and 33–35km along the Nile River; 9 and 30km near the Red Sea coast; 15 and 39km toward the western desert. The comprehensive comparison with previous crustal studies suggests that the main patterns of Moho undulations and the range of Moho depths are in good agreement with the previous crustal models in Egypt, as well as with the Bouguer gravity anomalies that well explain the Nile River sediments, Red Sea mountain belts and Western Desert depression and Oasis. The model of the Moho and Conrad discontinuities improves knowledge of the three dimensional structure of the crust beneath Egypt in wide areas where geophysical data is sparse.