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剩磁影响下的南海三维磁性结构反演策略
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Abstract:
磁力数据是研究南海海域深部结构、地质构造及构造演化的重要资料，南海海域三维磁性结构反演研究，将有助于为丰富和深化如上地质问题的认识提供定量的地球物理证据。然而由于南海地处低磁纬度区且南北跨度大，同时存在强剩磁影响，这些复杂因素的交织为南海磁测数据处理与反演提出巨大的挑战。为应对如上挑战，提出利用等效源技术与磁异常模量反演相结合的策略，开展南海海域三维磁性反演。考虑到低磁纬度、南北向磁倾角的剧烈变化以及地球曲率对频率域异常模量计算的影响，借助等效源技术可实现异常模量在空间域的稳定计算，继而基于模量数据进行三维模量反演，在剩磁影响和总磁化方向难以判定的情况下，可直接反演出地下的三维磁性分布。理论模型试验和南海东北部海区磁异常三维模量反演试算结果表明，等效源技术与磁异常模量反演相结合的策略是复杂条件下三维磁性反演的有效途径。
The magnetic data is an important data for studying deep crustal structures, regional geological structure, and tectonic evolution in South China Sea (SCS). The research of 3D magnetic structure inversion would help to provide the geophysical quantitative evidence for enriching and deepening the understanding of the above geological issues in SCS. However, the processing and inversion of magnetic data in SCS are faced with significant challenges due to intertwined influence factors, such as low magnetic latitudes, a large scale from south to north and the influence of strong remanent magnetization. To tackle these challenges, we present a comprehensive research strategy through the joint use of the equivalent source technique and amplitude inversion to construct 3D subsurface magnetism distribution from observed magnetic data. Firstly, in order to overcome the prohibitive difficulties in the wave-number domain due the low magnetic latitudes, dramatic changes of the magnetic inclination along longitude direction and the curvature of the earth, we use equivalent source technique to calculate the amplitude stably in the space domain. We then carry out amplitude inversion to generate 3D subsurface distribution of magnetization strength in the case that strong remanent magnetization is present and the general magnetization direction cannot be estimated. The test results of both synthetic model and field data in northern SCS demonstrate that the combined equivalent source technique and amplitude inversion is a feasible and effective approach to construct 3D magnetic structures under the complicated conditions in SCS.
| [1] | 姚伯初, 万玲, 曾维军, 等. 中国南海海域岩石圈三维结构及演化[M]. 北京: 地质出版社, 2006. |
| [2] | 郝天珧, 徐亚, 赵百民, 张永军, 彭利丽. 南海磁性基底分布特征的地球物理研究[J]. 地球物理学报, 2009, 52(11): 2763-2776. |
| [3] | Hansen, R.O. and Pawlowski, R.S. (1989) Reduction to the Pole at Low Latitudes by Wiener Filtering. Geophysics, 54, 1607-1613. https://doi.org/10.1190/1.1442628 |
| [4] | Keating, P. and Zerbo, L. (1996) An Improved Technique for Reduction to the Pole at Low Latitude. Geophysics, 61, 131-137. https://doi.org/10.1190/1.1443933 |
| [5] | Silva, J.B.C. (1986) Reduction to the Pole as an Inverse Problem and Its Application to Low-Latitude Anomalies. Geophysics, 51, 369-382. https://doi.org/10.1190/1.1442096 |
| [6] | Li, Y. and Oldeuburg, D.W. (2000) Reduction to the Pole Using Equivalent Sources. SEG Technical Program Expanded Abstracts, 19, 386-389. https://doi.org/10.1190/1.1816074 |
| [7] | Li, Y. and Oldeuburg, D.W. (2001) Stable Reduction to the Pole at the Magnetic Equator. Geophysics, 66, 571-578.
https://doi.org/10.1190/1.1444948 |
| [8] | 姚长利, 管志宁, 高德章, 张锡林, 张聿文. 低纬度磁异常化极方法——压制因子法[J]. 地球物理学报, 2003, 46(5): 690-696. |
| [9] | 骆遥, 薛典军. 基于概率成像技术的低纬度磁异常化极方法[J]. 地球物理学报, 2009, 52(7): 1907-1914. |
| [10] | Pautot, G., Rangin, C., Briais, A., et al. (1986) Spreading Direction in the Central South China Sea. Nature, 321, 150-154. https://doi.org/10.1038/321150a0 |
| [11] | Hayes, D.E. and Nissen, S.S. (2005) The South China Sea-Margins: Implications for Rifting Contrasts. Earth and Planetary Science Letters, 237, 601-61. https://doi.org/10.1016/j.epsl.2005.06.017 |
| [12] | Taylor, B. and Hayes, D.E. (1980) The Tectonic Evolution of the South China Basin. In: Hayes, D.E., Ed., The Tectonic and Geologic Evolution of Southeast Asian Seas and Islands, Part 1, Geophysical Monograph Series, Vol. 23, AGU, Washington DC, 89-104. https://doi.org/10.1029/GM023p0089 |
| [13] | Taylor, B. and Hayes, D.E. (1983) Origin and History of the South China Basin. In: Hayes, D.E., Ed., The Tectonic and Geologic Evolution of Southeast Asian Seas and Islands, Part 2, Geophysical Monograph Series, Vol. 27, AGU, Washington DC, 23-56. https://doi.org/10.1029/GM027p0023 |
| [14] | Briais, A., Patriat, P. and Tapponnier, P. (1993) Updated Interpretation of Magnetic Anomalies and Seafloor Spreading Stages in the South China Sea: Implications for the Tertiary Tectonics of Southeast Asia. Journal of Geophysical Research, 98, 6299-6328. https://doi.org/10.1029/92JB02280 |
| [15] | Li, C., Zhou, Z., Li, J., et al. (2008) Magnetic Zoning and Seismic Structure of the South China Sea Ocean Basin. Marine Geophysical Researches, 29, 223-238. https://doi.org/10.1007/s11001-008-9059-4 |
| [16] | 赵俊峰, 施小斌, 丘学林, 刘海龄. 南海东北部居里面特征及其石油地质意义[J]. 热带海洋学报, 2010, 29(1): 126-131. |
| [17] | Li, C., Zhou, Z., Hao, H., et al. (2008) Late Mesozoic Tectonic Structure and Evolution along the Present-Day Northeastern South China Sea Continental Margin. Journal of Asian Earth Sciences, 31, 546-561.
https://doi.org/10.1016/j.jseaes.2007.09.004 |
| [18] | Li, C.., Zhou, Z., Li, J., et al. (2007) Structures of the Northeastern Most South China Sea Continental Margin and Ocean Basin: Geophysical Constraints and Tectonic Implications. Marine Geophysical Researches, 28, 59-79.
https://doi.org/10.1007/s11001-007-9014-9 |
| [19] | Li, C.F., Shi, X., Zhou, Z.Y., et al. (2010) Depths to the Magnetic Layer Bottom in the South China Sea Area and Their Tectonic Implications. Geophysical Journal International, 182, 1229-1247.
https://doi.org/10.1111/j.1365-246X.2010.04702.x |
| [20] | Li, Y.G., Shearer, S., Haney, M., et al. (2010) Comprehensive Approaches to 3D Inversion of Magnetic Data Affected by Remanent Magnetization. Geophysics, 75, L1-L11. https://doi.org/10.1190/1.3294766 |
| [21] | Shearer, S. and Li, Y.G. (2004) 3D Inversion of Magnetic Total-Gradient Data in the Presence of Remanent Magnetization. 74th Annual International Meeting, SEG, Expanded Abstracts, 774-777. https://doi.org/10.1190/1.1851318 |
| [22] | 管志宁. 地磁场与磁力勘探[M]. 北京: 地质出版社, 2005. |
| [23] | Dampney, C.N.G. (1969) The Equivalent Source Technique. Geophysics, 34, 38-53. https://doi.org/10.1190/1.1439996 |
| [24] | Li, Y.G. and Oldenburg, D.W. (1998) 3-D Inversion of Gravity Data. Geophysics, 63, 109-119.
https://doi.org/10.1190/1.1444302 |
| [25] | Li, Y.G. and Oldenburg, D.W. (1996) 3-D Inversion of Magnetic Data. Geophysics, 61, 394-408.
https://doi.org/10.1190/1.1443968 |
| [26] | Li, Y.G. and Oldenburg, D.W. (2010) Rapid Construction of Equivalent Sources Using Wavelets. Geophysics, 75, L51-L59. https://doi.org/10.1190/1.3378764 |
| [27] | 李春峰, 汪品先, 等. 南海张裂过程及其对晚中生代以来东南亚构造的启示——IODP建议书735-Full介绍[J]. 地球科学进展, 2009, 24(12): 1339-1351. |
| [28] | 高金耀, 吴招才, 王健, 杨春国, 张涛. 南海北部陆缘磁静区及与全球大洋磁静区对比的研究评述[J]. 地球科学进展, 2009, 24(6): 577-587. |
| [29] | 周蒂, 王万银, 庞 雄, 王家林, 蔡东升, 孙珍. 地球物理资料所揭示的南海东北部中生代俯冲增生带[J]. 中国科学(D辑): 地球科学, 2006, 36(3): 209-218. |
| [30] | 胡登科, 周蒂, 吴湘杰, 何敏. 南海东北部高磁异常带成因的地球物理反演研究[J]. 热带海洋学报, 2008, 27(1): 32-37. |
| [31] | 姚伯初, 万玲, 吴能友. 南海新生代构造演化及岩石圈三维结构特征[J]. 地质通报, 2005, 24(1): 1-8. |
