Forward modeling for 2D body gravity anomaly in the space-wavenumber mixed domain
(2.School of Geosciences and Info-physics, Central South University, Changsha, Hunan Province, China 410083)
(3.Guangdong Electric Power Design Institute, China Energy Engineering Group Co., Ltd., Guangzhou, Guangdong Province, China 510663)
(4.College of Earth Sciences, Guilin University of Technology, Guilin, Guangxi Province, China 541004)
(5.No. 1 Daqing Geophysical Exploration Company of BGP, CNPC, Daqing, Heilongjiang Province, China 163357)
【Abstract】An efficient and high-precision forward modeling of 2D body gravity anomaly in a space-wavenumber mixed domain is proposed to calculate the gravity anomaly in the case of arbitrary density distribution. Processed by 1D Fourier transform, 2D partial differential equation governing gravity potential in the spatial domain is transformed into a group of independent 1D differential equations engaged with different wavenumbers. The method preserves the vertical direction in the spatial domain, so shallow and deep meshes for modeling can be fine and coarse respectively. By this way, both the accuracy and the efficiency of calculation are taken into account. The 1D finite element method is used to solve the transformed differential equations with different wavenumbers. Moreover, the efficiency of solving linear equations with a fixed bandwidth assembled by the finite element analysis is further improved by a chasing method. To test the proposed algorithm, a constant-density 2D model and a variable-density 2D model are designed. Numerical test results show that the proposed algorithm not only guarantees the calculation accuracy but improves the calculation efficiency compared with the conventional methods.
【Keywords】 gravity anomaly; space-wavenumber mixed domain; 2D body; forward modeling;
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