考虑关断时间的地面瞬变电磁三维带地形反演  

Three-dimensional ground TEM inversion over a topographic earth considering ramp time

作　　者：齐彦福 智庆全 李貅[1,2] 景旭 戚志鹏[1,2] 孙乃泉[1,2] 周建美[1,2] 刘文韬[1,2] QI YanFu;ZHI QingQuan;LI Xiu;JING Xu;QI ZhiPeng;SUN NaiQuan;ZHOU JianMei;LIU WenTao(College of Geological Engineering and Geomatics,Chang′an University,Xi′an 710054,China;Integrated Geophysical Simulation Laboratory,Chang′an University,Xi′an 710054,China;Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Sciences,Hebei Langfang 065000,China)

机构地区：[1]长安大学地质工程与测绘学院,西安710054 [2]长安大学地球物理场多参数综合模拟实验室,西安710054 [3]中国地质科学院地球物理地球化学勘查研究所,河北廊坊065000

出　　处：《地球物理学报》2021年第7期2566-2577,共12页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41830101,42004118,42074168,41704108);中国博士后科学基金面上项目(2018M643553);中央级公益性科研院所基本科研业务专项(AS2020J01);“深地资源勘查开采”重点专项(2018YFC0603803)联合资助.

摘　　要：起伏地形和关断时间对地面瞬变电磁响应影响严重,这给传统基于水平地表模型和理论阶跃波形的瞬变电磁数据解释技术带来很大困难.为此,本文开展考虑起伏地形和关断时间的地面瞬变电磁三维反演算法研究.正演采用基于非结构网格和后退欧拉隐式时间离散格式的时间域有限元算法,快速模拟起伏地表模型瞬变电磁响应.反演采用L-BFGS算法,减少每次反演迭代的计算量.针对发射线圈随地表起伏变化的特点,利用基于偶极子离散的场源处理技术模拟发射源的实际形状,采用瞬时电流脉冲技术实现考虑关断时间的地面瞬变电磁三维正演模拟.我们首先将本文开发的三维反演算法应用于理论模型的反演计算中,检验本文算法的可靠性,并分析地形和关断时间对反演结果的影响特征.在此基础上,进一步将本文算法应用于实测数据反演,验证本文算法的实用性.The topography and transmitting ramp time has serious effects on the ground transient electromagnetic(TEM)data,which brings big challenges to the traditional TEM interpretations based on a flat earth and step waveform.In this article,we develop a 3D ground TEM inversion algorithm over a topographic earth model considering ramp time.The time-domain finite-element method,based on unstructured mesh and Back-ward Euler scheme,is used to quickly simulate the TEM responses over a topographic earth.Furthermore,we adopt the L-BFGS method for our inversion to reduce the amount of calculation in each inversion iteration.We adopt the source processing technology based on dipole discretization technique to simulate the complex shape of the transmitting loop caused by topography.And then the instantaneous current pulse technology is used to modeling the TEM response considering ramp time.We first apply our 3D inversion codes to the synthetic data to verify its reliability and analyze the effects of topography and ramp time on the inversion results.Finally,we further apply our algorithm to the field data to check its usefulness.

关 键 词：地面瞬变电磁 三维反演 地形 关断时间 

分 类 号：P631[天文地球—地质矿产勘探]