Abstract
Satellite and airborne gravity and magnetic data are gathered away from the earth's surface, and the resolution is usually insufficient to describe the geological structures in detail. Therefore, downward continuation is typically used to enhance small-scale sources and improve spatial resolution to interpret potential field data. To further improve the stability and accuracy of the downward continuation, we present a new strategy based on the continued fraction approximation in the wavenumber domain. We established our method based on the relationship of the Taylor series and the continued fraction in the wavenumber domain. According to the comparison of different terms of the continued fraction, we found that a reasonable number of terms needs to be calculated using the continued fraction. In this way, stable results that are insensitive to noise can be obtained with the new method. Compared with the typical Taylor series method in the wavenumber domain, the improved Taylor series method, and the Tikhonov regularized downward continuation method, our new method is less sensitive to noise. The results demonstrated that continued fraction can be used to replace the classical Taylor series expansion with reasonable terms to implement more accurate and stable downward continuation. Finally, the new method was applied to reduced-to-pole total fields of aeromagnetic anomalies from the Xuanhua-Huailai area, and the results showed its superiority compared with the other methods. With the new downward continuation method, the small-scale anomalies and the structure distributions are more obvious and better depicted. The results are in good agreement with geological depictions.
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Data Availability Statement
The data are unavailable to the public and have restricted access due to the regulations from the Chinese Geological Survey.
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Acknowledgements
This research was partly supported by the National Natural Science Foundation of China (42004068, 41904122), the Second Tibetan Plateau Scientific Expedition and Research Program (Grant No. 2019QZKK0704), China Geological Survey’s project (DD20189642, DD20190012 and DD 20190129), the Science and Technology Plan of Gansu Province (20JR5RA251), and the Special Project for Basic Scientific Research Service (JYYWF20180101 and JKY202007).
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WZ: Methodology, software, formal analysis, visualization, writing—original draft, review and editing, funding acquisition, supervision. CZ: formal analysis, visualization, writing—original draft, review & editing, funding acquisition. DZ: methodology, review & editing, validation, writing—review & editing, funding acquisition.
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Zhou, W., Zhang, C. & Zhang, D. A Novel Downward Continuation Method Based on Continued Fraction in Wavenumber Domain and Its Application on Aeromagnetic Data in the Xuanhua-Huailai Area, China. Pure Appl. Geophys. 179, 777–793 (2022). https://doi.org/10.1007/s00024-021-02937-2
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DOI: https://doi.org/10.1007/s00024-021-02937-2