全球岩石圈磁异常模型研究进展与挑战

Progress and challenges in modeling global lithospheric magnetic anomalies

通过半个多世纪的航空磁测和海洋磁测数据采集,近地表磁测数据几乎覆盖全球,相继编绘了国家和洲际尺度的磁异常图.进入21世纪,以CHAMP为代表的卫星磁测技术提供了全球尺度下的长波磁异常背景,建立了《世界磁异常图》等以弧分为分辨率的全球磁异常网格,并以此构建了岩石圈磁场高斯球谐系数模型,例如NGDC-720模型.尽管全球岩石圈磁异常模型在空间分辨率等方面取得了巨大进步,反映的最短波长从上百千米提升至几十千米,但仍面临巨大挑战,例如实际精度仅能达到上百纳特.为此,本文回顾了国家尺度到全球尺度磁异常汇编情况,讨论了磁异常处理与汇编的关键技术.同时,也分析了全球岩石圈磁场建模的难点,旨在克服当前的局限性,实现岩石圈磁场模型自主、可控.

Over the past 50 years,extensive airborne and oceanic magnetic survey data collection efforts have resulted in the almost complete coverage of near-surface magnetic survey data worldwide.National and intercontinental magnetic anomaly maps have also been generated.Advancements in satellite magnetic field measurements,such as those from CHAllenging Minisatellite Payload(CHAMP),provided longwave magnetic anomaly backgrounds on a global scale.This has led to the realization of global magnetic anomaly grids with arcminute resolutions,such as the World Digital Magnetic Anomaly Map(WDMAM).Utilizing these datasets,spherical harmonic coefficient models such as the NGDC-720 model have been established for lithospheric magnetic fields.The global lithospheric magnetic anomaly model has progressed considerably;for example,the shortest wavelengths reflected in the spatial resolution have improved from hundreds of kilometers to tens of kilometers.However,modeling still faces major challenges;for example,the accuracy of the model remains low,amounting to a few hundred nanotesla.In this study,we provide a comprehensive review of the techniques for compiling magnetic anomalies at various scales and discuss the key methodologies for processing and compiling them.Furthermore,we address the complexities involved in modeling the global lithospheric magnetic field.Our objective was to address the shortcomings of lithospheric magnetic anomaly modeling and develop a high-precision,independent,and controllable lithospheric magnetic field model for China.