Synthetic study of 2.5-D ATEM based on finite element method
QIANG Jian-Ke1, ZHOU Jun-Jie2, MAN Kai-Feng1
1. Shool of Central South University, Central South University, Changsha 410083, China;
2. Beijing Research Institute of Uranium Geology, Beijing 100029, China
Based on the triangular mesh dissection of the finite element method, this paper presents the 2.5-D airborne transient electromagnetic method forward modeling. Firstly the time domain electromagnetic partial equations are converted into laplace domain with the numerical time-frequency transform algorithm, then the 2.5-D expressions are obtained from 3-D case by adopting the fourier transform. The airborne data are acquired from the results of the digital inverse laplace transform of the 2-D electric and magnetic components in laplacian domain, which is computed using finite element method.Instead of the conventional algorithm, the anomalous field method is employed throughout the finite element process, so that the source singularity of total field is avoided. the source impact is embodied in the differencial equation by appling the background electromagnetic field item.The computing accuracy and efficiency would be managed rigorously due to the wide dynamic range of the transient singnal, as well as the two-time inverse laplace and fourier transforms. Otherwise the accumulative error will soar acceptably. The synthetic model experiments shows that the numeric modeling solutions match the analytical results of homogeneous and layered erath responses well, which also proves the effectiveness of the algorithm.
强建科, 周俊杰, 满开峰. 时间域航空电磁法2.5维有限元模拟[J]. 物探与化探, 2015, 39(5): 1059-1062.
QIANG Jian-Ke, ZHOU Jun-Jie, MAN Kai-Feng. Synthetic study of 2.5-D ATEM based on finite element method. Geophysical and Geochemical Exploration, 2015, 39(5): 1059-1062.
[1] Nabighian M N.Quasi-static transient response of a conducting half space:An approximate representation[J].Geophysics,1979,44(9):1700-1705.[2] Fullagar P K.Generation of conductivity-depth parasections from coincident loop and in-loop TEM data[J].Exploration Geophysics,1989,20:43-45.[3] Keating P,Crossley D.The inversion of time-domain airborne electromagnetic data using the plate model[J].Geophysics,1990,55(6): 705-711.[4] Zhdanov M S,Pavlov D,Ellis R.Localized S-inversion of time domain electromagnetic data[J].Geophysics,2002,67(4):1115-1125.[5] Huang H,Rudd J.Conductivity-depth imaging of helicopter-borne TEM data based on a pseudolayer half-space model[J].Geophysics,2008,73(3):F115-F120.[6] Huang H,Palacky G J.Damped least-squares inversion of time-domain airborne EM data based on singular value decomposition[J].Geophysical Prospecting,1991,39:827-844.[7] Paterson N R,Grant F S,Misener D J.Development of computer software for geophysical interpretation,in Pye.E.G.,and Barlow,R.B.,Eds.,Exploration technology development program for the Board of Industrial Leadership and Development: Summary of research 1981—1983[J].Ontario Geol.Surv.miscellaneous paper,1983,115:53-61.[8] Sattel D.Inverting airborne electromagnetic(AEM) data with Zohdy's Method[J].Geophysics,2005,80:77-85.[9] 李永兴,强建科,汤井田.航空时间域电磁法一维正反演研究[J].地球物理学报,2010,53 (3):751-759.[10] 强建科,李永兴,龙剑波.航空瞬变电磁数据一维Occam反演[J].物探化探计算技术,2013,35(5):501-505.[11] 罗勇.时间域航空电磁一维正反演研究[D].成都:成都理工大学,2013.[12] 毛立峰,陈斌,吕东伟.测高数据不准时的直升机航空瞬变电磁一维反演方法理论研究[J].物探与化探,2011,35(3):402-405.[13] Stoyer C H,Greenfield R L.Numerical solutions of the response of a two dimensional earth to an oscillating magnetic dipole source[J].Geophysics,1976,41:519-530.[14] Sugeng F,Raiche A,Rijo L.Comparing the time-domain EM response of 2-D and elongated 3-D conductors excited by a rectangular loop source[J].Geomag and Geoelec,1993,45:873-885.[15] Raiche,A P.Modelling the time-domain response of AEM systems[J].Expl Geophys,1998,29:103-106.[16] Annetts D,Raiche A,Sugeng F.The time-domain electromagnetic response of wedge-like structures[C]//ASEG 17th Geophysical conference and exhibition,Sydney 2004.[17] Wilson G,Raiche A,Sugeng F.Practical 3D AEM inversion using 2.5D modeling[C]//AESC 2006,Melbourne,Australia,2006.[18] Wilson G,Raiche A,Sugeng F.2.5D inversion of airborne electromagnetic data[J].Exploration Geophysics,2006,37:363-371.[19] Viezzoli A,Auken E,Munday T.Spatially constrained inversion for quasi 3D modeling of airborne electromagnetic data:an application for environmental assessment in the Lower Murray Region of South Australia[J].Exploration Geophysics,2009,40:173-183.[20] Meng Y,Li W,Zhdanov M,et al.2.5-D electromagnetic forward modeling in the time and frequency domain using the finite-element method[C]//SEG 69th Annual Meeting Extended abstracts,USA,1999.[21] 罗延钟,张胜业,王卫平.时间域航空电磁法一维正演研究[J].地球物理学报,2003,46(5):719-724.[22] 林君,稽艳鞠,于生宝.ATEM-Ⅱ型瞬变电磁系统的实际应用[J].物探与化探,2004,28(6):496-499.[23] 王卫平,王守坦.吊舱式直升机频率域电磁系统在北京密云红光铁矿的勘查效果[J].物探与化探,2006,30(5): 420-426.[24] 刘桂芬.回线源层状大地航空瞬变电磁场的理论计算[D].长春:吉林大学,2008.[25] 周俊杰.航空瞬变电磁2.5维有限元正演模拟[D].长沙:中南大学,2011.[26] 强建科,罗延钟,汤井田,等.航空瞬变电磁法关断电流斜坡响应的计算[J].地球物理学进展,2012.2,27(1):345-351.[27] 许洋铖,林君,李肃义,等.全波形时间域航空电磁响应三维有限差分数值计算[J].地球物理学报,2012,55(6):2105-2114.[28] 龙剑波,强建科.航空瞬变电磁一维正演的连分式算法研究,[J].湖南科技大学学报:自然科学版,2013,28(4):86-91.[29] 殷长春,黄威,贲放.时间域航空电磁系统瞬变全时响应正演模拟[J].地球物理学报,2013,56(9):3153-3162.[30] 王宇航.吊舱式时间域直升机航空电磁2.5维正演及响应曲线分析[D].成都:成都理工大学,2013.[31] 田培培.时域航空回线源的三维异常体电磁响应探测分辨率研究[D].长春:吉林大学,2013.
