Lithospheric analysis of satellite geopotential anomalies of East Asia

Satellite gravity and magnetic anomalies are used to study the lithosphere of East Asia. Free-air gravity anomalies are decomposed into terrain-correlated, mantle/core and intracrustal components by spectral correlation analysis of the free-air gravity anomalies and terrain gravity effects. Compensated terrain gravity anomalies are obtained by removing the terrain-correlated free-air gravity anomalies. They are used to estimate the Moho undulation and crustal thickness by Gauss-Legendre quadrature (GLQ) inversion techniques assuming a Airy-Heiskanen model of crustal compensation.; These results are used to develop enhanced reduction procedures to generate an improved Magsat magnetic anomaly map for East Asia. A degree 12 core field is removed from the data that are updated for the crustal components in the core field differences between degree 14 and 12. These components are estimated by using spectral correlation analysis to compare the Magsat anomalies to the magnetic effect of the crust that is available from the first vertical derivative of the terrain-correlated free-air gravity anomalies via Poisson's theorem. External field effects are separated using pass-by-pass correlation analysis of the dusk and dawn data sets and their spectral reconstruction. Coherent components in the dusk and dawn maps are combined to estimate the magnetic anomalies of the lithosphere.; Long wavelength magnetic features related to lower crustal thickness variations are converted into effective magnetization contrasts by a new GLQ inversion technique. Effective magnetization contrasts of the lower crust range over {dollar}pm{dollar}4 A/m in accordance petrological studies.; Finally, a new GLQ integration formula for triangular wedge sources is derived for modeling of satellite-altitude geopotential field anomalies from arbitrarily shaped sources. Detailed magnetization and density contrasts for central India, the Tibetan Plateau, and the Bengal Gulf region are modeled by this new formula. Positive magnetic and negative gravity anomalies over India may reflect ancient cratonic features with positive and negative contrasts in crustal magnetization and density, respectively. The modeling for the Tibetan Plateau suggests a demagnetized crust that is consistent with a Curie isotherm that may be upwarped into the middle crust and infers a positive density contrast related to the uplift of dense mantle material into the crust. Modeling the negative geopotential anomalies of the Bengal Gulf indicates the possible presence of an elevated Curie isotherm in the crust and related hydrothermal alteration due to the presence of thick sediments or compositional variations.