Geoscience Reference
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Fig. 4.3
The gravimetric Moho solution computed globally on a 1
1 arc-deg grid
4.5
Discussion and Concluding Remarks
The consolidated crust-stripped gravity disturbances have a maximum correlation
with the Moho geometry. However, uncertainties of a crustal structure model
contribute to the total error budget. Tenzer et al. (
2012a
) estimated that relative
errors in computed values of the consolidated crust-stripped gravity data can reach
about 10 %. Moreover, these gravity data still comprise a long-wavelength signal
from unmodeled mantle heterogeneities. Bagherbandi and Sjöberg (
2012
) proposed
a procedure of treating the long-wavelength gravity signal of the mantle in solving
the VMM inverse problem of isostasy. They applied the method of Eckhardt (
1983
)
to estimate the maximum degree of long-wavelength spherical harmonic terms,
which should be removed from the gravity field in prior of solving the VMM
problem. The principle of this procedure was based on finding the representative
depth of gravity signal attributed to each spherical harmonic degree term. The
spherical harmonics, which have the depth below a certain limit (chosen, for
instance, as the maximum Moho depth), are then removed from the gravity field.
The estimation of the Moho depth uncertainties is not simple, because there is not
enough information on the accuracy of input data. The expected largest uncertainties
in the estimated Moho depths are mainly due to the inaccuracies of crustal models
currently available and unmodeled mantle heterogeneities. The relative errors in
computed values of the consolidated crust-stripped gravity data of about 10 % yield
similar relative uncertainties in the estimated Moho depths, provided that the gravity
errors propagate almost linearly into the Moho errors. Most of these errors are due
to large uncertainties in the CRUST2.0 sediment and consolidated crust data, while
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