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2 Acta Geophysica

2 2011

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Smoothing impact of isostatic crustal thickness models on local integral inversion of satellite gravity gradiometry data

Eshagh M., Bagherbandi M.

Acta Geophysica

2011

Vol. 59, no. 5

891-906

The effects of topographic masses on satellite gradiometric data are large and in order to reduce the magnitude of these effects some compensation mechanisms should be considered. Here we use the isostatic hypotheses of Airy-Heiskanen and the recent Vening Meinesz-Moritz for compensating these effects and to smooth the data prior to their downward continuation to gravity anomaly. The second-order partial derivatives of extended Stokes' formula are used for the continuations over a topographically rough territory like Persia. The inversions are performed and compared based on two schemes of the remove-compute-restore technique and direct downward continuation. Numerical results show that the topographic-isostatic effect based on Vening Meinesz-Mortiz's hypothesis smoothes the data better than that based on Airy-Heiskanen's hypothesis. Also the quality of inversions of the smoothed data by this mechanism is twice better than that of the nonsmoothed ones.

A method of estimating the Moho density contrast with a tentative application of EGM08 and CRUST2.0

Sjoberg L., Bagherbandi M.

Acta Geophysica

2011

Vol. 59, no. 3

502-525

Based on Vening Meinez-Moritz global inverse isostatic problem, the Moho density contrast is formulated as that of finding a solution of a Fredholm integral equation of the first kind. We present solutions to this equation by combining global models of gravity (EGM08), topography (DTM2006) and seismic crust (CRUST2.0) to a resolution of 2° x 2°. The test computations yielded Moho density contrasts ranging from 81.5 kg/m3 (in Pacific) to 988 kg/m3 (Tibet), with averages of 678 ± 78 and 334 ± 108 kg/m3 for continental and oceanic regions, respectively, and a global average of 448 ± 187 kg/m3. Estimated Moho depths range from 8 to 75 km with continental and oceanic averages of 36.6 ± 5.3 km and 12.9 ± 5.8 km, respectively, and a global average of 21 ± 12.5 km. This article has its emphasis on the new theory, while significant corrections to computational results are expected in a forthcoming study, where the isostatic gravity anomaly will be reduced for several disturbing signals.