【作者】 敖文波； 周蒂； 胡光道；

【Author】 AO Wenbo~(1,2),ZHOU Di~2,HU Guangdao~1 (1.China University of Geosciences,Wuhan 430074,China;2.South China Sea Institute of Oceanology, The Chinese Academy of Sciences,Guangzhou 510301,China;3.Nuclear Industry Bureau of Geology of Guangdong Province,Guangzhou 510800,China)

【机构】 中国地质大学(武汉)资源学院； 中国科学院南海海洋研究所； 广东省核工业地质局；

【摘要】 在对南沙海域及邻区(2°N～17°N,104°E～122°E)1960～2000年间地磁倾角/偏角等地磁要素特征变化及ΔT磁异常数据特点分析研究的基础上,通过对低纬度化极方法的综合分析及实验对比试算,提出了滤波与偏移抽样法结合的化极处理方法模式及数据分带划块的具体实施措施,实现了该超低磁纬区,亦称零磁纬区(地磁倾角变化范围:-15°～+20°;地磁偏角变化范围:-1°～+1.3°)大范围、多来源、长测量时间间隔实测ΔT磁异常的变倾角变偏角化极,并给出了对化极结果的评价及验证。ΔT磁异常化极的实现,为深入研究该区域内磁性地质体特征,提供了更为密切直接的依据。更多还原

【Abstract】 The solution of reduction-to-the-pole(RTP) of magnetic data in the wavenumber domain faces a long standing difficulty of instability and distortion when the observed data are acquired at low magnetic latitudes or at the equator.The southern South China Sea(2°N～17°N, 104°E～122°E) is the area of ultra-low magnetic latitudes including the magnetic equator,with the geomagnetic inclination in the range of-15°～+ 20°.AvailableΔT magnetic anomaly data for the area were compiled from measurements by different organizations during the years from 1960 to 2000.The possible systematic and other errors involved in the compilation have added difficulties for performing RTP. We developed a procedure to this problem that allows a stable reconstruction of the RTP field with a high fidelity in the whole research area,even at the magnetic equator.The solution is obtained by the effective combination of filtering and biased sampling theory which is a theory about algorithm and calculation errors of Fourier transform;Filtering is used first to eliminating the noise in the observed magnetic data,then biased sampling is used to inverting the Fourier transform of the filtered data in the wavenumber domain.The area is divided into small(1×2or 1×1km~2) cells so that in each cell the magnetic inclination and declination relatively constant. All the procedures of RTP are performed with the aid of GIS platform. The pattern of magnetic fields for the southern South China Sea changed significantly after RTP.The Curie interface estimated from theΔT data after RTP shows a trend of shoaling from shelf area to the deep-sea basin and thus is more reasonable than the reversed trend obtained from the originalΔT data.This to a certain extend shows the validity of the new RTP procedure.更多还原