**6. Discussion and final remarks**

The study of the Moho discontinuity has been a crucial topic in inferring the dynamics of the Earth's interior for a long time. In general, the Moho can be studied with profitable results through seismic data. However, due to the sparsity of seismic data in parts of the world, it has not been well determined. With the advent of satellite missions, it has been possible to recover the Moho constituents via satellite gravity observations based on an isostatic model.

So far, various isostatic models have been presented for recovering the Moho constituents, but it was not clarified which one is most appropriate to employ for geophysical and geodynamical purposes. The preliminary and simplest isostatic models proposed are the classical ones with local or regional compensation. However, those models cannot realistically image the actual Moho undulation. This is because they assume a uniform crustal density, disregarding the density irregularities distributed within the crust and sub-crust. Understanding this important role of Moho recovery has been in the center of the discussions by many geoscientists during the last decades.

Here we have determined the Moho constituents and their uncertainties based on the VMM technique using both gravimetric and seismic data on a global scale to a resolution of 1° � 1°. The combination of the gravimetric and seismic data in one approach as well as the joint adjustment of MD and density contrast are expected to significantly improve the total result.

The basic VMM method is based on the hypothesis that the isostatic gravity disturbance vanish. However, this is the case only if the gravity component is reduced such that there are no signals from the Earth's interior below the crust. The major problem in this reduction is therefore to distinguish and remove those signals, which we utilize by estimating and removing the NIEs with the help from CRUST1.0 seismic model.

The second step is to combine the gravimetric data, propagated in the VMM technique to a linear equation (with MD and MDC as the unknowns), with a seismic model, CRUST1.0. This is performed by a weighted least-squares adjustment, block by block, which has the advantage that the standard error of the unknowns can also be estimated block-wise. The weights of the gravity disturbances were based on the error estimates by Eq. (23), while the weights for CRUST1.0 data were those published in [12].

*On Moho Determination by the Vening Meinesz-Moritz Technique DOI: http://dx.doi.org/10.5772/intechopen.97449*

Our estimated results can be summarized as follows. The global means of MD and MDC are 23.8 � 0.05 km and 340.5 � 0.37 kg/m<sup>3</sup> , respectively, ranging between 7.6–70.3 km and 21.0–650.0 kg/m<sup>3</sup> . The MD results were validated by the recent CRUST19 seismic model, showing that the differences between the models vary within the extremes �23.4 and 32.9 km, with a global average of 0.91 km and an RMS fit of 4 km. The normalized differences were generally within the limits �1, which should be regarded as acceptable.
