摘要
电性源短偏移距瞬变电磁法是近年来新提出的固体矿产深部电磁探测方法之一,较传统的回线源瞬变电磁具有探测深度深、仪器轻便和分辨率高等优点。但该方法由于偏移距较短,距发射源较近,正演中的频-时转换会受到转换方法及其他工作参数的影响,进而直接影响探测结果,因此有必要开展频-时转换效果分析评价。通过对影响频-时转换的因素以及常用的四种频-时转换方法(Guptasarma线性滤波法、折线逼近法、余弦变换的数值滤波法和正弦变换的数值滤波法)在电性源短偏移距瞬变电磁正演响应计算中的对比,从计算时间和转换精度两方面分析了在不同条件下的转换效果,为一维及高维度的瞬变电磁正演计算提供频-时转换方法参考。对比结果表明:1)影响时间域瞬变电磁场正演计算(即频-时转换效果)的精度不仅和转换方法本身有关,而且也和偏移距及地下介质电阻率等参数有关;2)通过正演模拟,在低阻探测区采用折线逼近法与正弦变换的数值滤波法相对Guptasarma线性滤波法和余弦变换的数值滤波法转换精度更高,整体误差更小,而Guptasarma线性滤波法的计算速度最快,早期计算精度较高,晚期计算精度较差;在高阻探测环境中,采用折线逼近法计算精度和速度均相对较好,Guptasarma线性滤波法、正弦变换的数值滤波法及余弦变换的数值滤波转换效果均较差,特别是在晚期。因此,对于未知的探测区域,若实现高精度的电性源瞬变电磁正演计算,采用折线逼近法进行频-时转换相对效果最佳。
Short offset transient electromagnetic method with electrical source is one of the newly proposed deep electromagnetic detection methods for solid mineral resources in recent years.Compared with traditional loop source transient electromagnetic method,it has the advantages of large detection depth,lightweight instrument,and high resolution.However,due to its short offset distance and close distance to the emission source,its efficiency and accuracy need to be carefully considered during frequency time conversion,especially in areas with high resistivity.This article compared the factors that affect frequency time conversion and four commonly used frequency time conversion methods(Guptasarma linear filtering method,line approximation method,cosine transform numerical filtering method,and sine transform numerical filtering method)in the forward calculation of short offset transient electromagnetic waves in electrical sources.The conversion effects of each method under different conditions were analyzed from the perspectives of calculation time and conversion accuracy,so as to provide a reference for frequency time conversion methods for one-dimensional and high-dimensional transient electromagnetic forward modeling calculations.The comparison results show that:1.The accuracy of forward calculation of transient electromagnetic fields in the time domain(i.e.frequency time conversion effect)is not only related to the conversion method itself,but also to parameters such as offset and underground medium resistivity.The smaller the offset distance,the worse the frequency time conversion effect.The higher the resistivity of the underground medium,the worse the frequency time conversion effect.Therefore,in high resistance detection areas,the use of short offset electrical source transient electromagnetic method requires frequency time conversion;2.In the low resistance detection area,the numerical filtering method using line approximation and sine transform has higher conversion accuracy and overall smaller errors compared
作者
胡英才
王瑞廷
李貅
sourceHU Yingcai;WANG Ruiting;LI Xiu(Northwest Nonferrous Geological and Mining Group Co.Ltd.,Xi’an 710054,China;College of Geology Engineering and Geomatics,Chang’an University,Xi’an 710061,China;CNNC Key Laboratory of Uranium Resources Exploration and Evaluation Technology Beijing Research Institute of Uranium Geology,Beijing 100029,China)
出处
《世界核地质科学》
CAS
2024年第2期299-311,共13页
World Nuclear Geoscience
基金
西北有色地质矿业集团博士后科研工作站项目资助(编号:XBDKKJ202111)
国家自然科学基金项目(编号:41604126)
重点勘查区铀资源前景评价研究(物探部分)(编号:物D2219-1)联合资助。
