Electromagnetic divergence correction for 3D anisotropic EM modeling |
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| Institution: | 1. GEUS — Geological Survey of Denmark and Greenland, Øster Voldgade 10, Copenhagen DK-1350, Denmark;2. GEOMAR — Helmholtz Centre for Ocean Research, Wischhofstrasse 1-3, 24148 Kiel, Germany;3. University of Leicester, Department of Geology, LeicesterLE1 7RH, United Kingdom;4. University of Durham, Department of Earth Sciences, DurhamDH1 3LE, United Kingdom;1. Department of Land Management, Zhejiang University, Hangzhou 310058, China;2. Jangho Architecture College, Northeastern University, Shenyang 110169, China;3. Institute for Environmental Studies (IVM), VU University Amsterdam, Amsterdam, 1081HV, the Netherlands |
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| Abstract: | Until now, the application of divergence correction has been focusing on the electromagnetic (EM) isotropic modeling. However, in regions where the earth demonstrates strong electrical anisotropy due to lamina or faults saturated with water, the traditional divergence corrections may not be working for EM modeling. In this paper, based on the divergence-free property of the current density, we propose a divergence correction technique to speed up the EM modeling process for a 3D arbitrarily anisotropic earth. The volume current density weighting method is adopted for the discretization of divergence correction, so it can be applied to non-uniform grid model. By enforcing the constraints associated with the divergence-free property, the quasi-minimal residual (QMR) iterations and the total computational time for the EM modeling are largely reduced. Furthermore, we discuss how to divide the QMR process into sections and the influence of the number of iterations and the normalized residual on the solution process. We take a helicopter-borne EM system over a 3D earth with arbitrarily electrical anisotropy as an example to examine the effectiveness of our anisotropic divergence correction technique on the EM modelings. |
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