Gravimetric geoid for Egypt implementing Moho depths and optimal geoid fitting approach

The aim of this paper is to investigate the effect of implementing the experimentally determined GEMMA Moho depths (GOCE Exploitation for Moho Modeling and Applications), which are partly seismically estimated, in gravimetric geoid computation in Egypt. The window remove-restore technique has been proposed to avoid the double consideration of the topographic-isostatic masses in the neighbourhood of the computational point. The plate loading theory has been used to model the seismically determined Moho depths. A constant density contrast between the lower crust and the upper mantle has been postulated. The tailored geopotential model EGTGM2014 has been used for the long wavelength contributions of the Earth's gravity field. A comparison with a geoid computed using the EGM2008 and Airy floating hypothesis has been made. For all cases, a gravimetric geoid for Egypt has been computed using Stokes' integral in the frequency domain by 1-D FFT technique. The computed geoids are fitted to the GPS-levelling derived geoid using an optimum geoid fitting technique for Egypt introduced by the author. The results show that using the seismically determined Moho depths within the plate loading theory and the EGTGM2014 tailored geopotential model gives a geoid with external accuracy of about 16 cm.