Three dimensional inversion of multisource time domain electromagnetic data
Three dimensional inversion of multisource time domain electromagnetic data
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DOI：
10.1190/geo2012-0131.1
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发表时间：
2013
期刊：
影响因子：
3.3
通讯作者：
D. Oldenburg;E. Haber;R. Shekhtman
中科院分区：
文献类型：
--
作者：
D. Oldenburg;E. Haber;R. Shekhtman
提出了一种多源时间域电磁数据的三维反演方法。正演模型由时间上的麦克斯韦方程组成，其中磁导率是固定的，但电导率可以是高度不连续的。反演的目的是恢复给定的电场和/或磁场测量的电导率。矩阵分解软件和高性能计算的出现使我们能够使用直接求解器来解决3D时间域电磁问题。当来自许多发射机和几十年的数据可用时，这是特别有利的。我们首先用磁场H表示麦克斯韦方程，然后在空间上用有限体积法离散，在时间上用倒向欧拉方法离散。正向算子是对称正定的，并且可以利用分布在处理器阵列上的工作来执行Cholesky分解。使用因式分解算子可以快速地执行正演模拟。节省的时间是相当可观的，它们使大型地面或机载数据集的3D反演成为可能。这是通过使用合成例子和通过对在墨西哥大型硫化物矿床圣尼古拉斯获得的多源UTEM场数据集进行反演来说明的。
We present a 3D inversion methodology for multisource time-domain electromagnetic data. The forward model consists of Maxwell’s equations in time where the permeability is fixed but electrical conductivity can be highly discontinuous. The goal of the inversion is to recover the conductivitygiven measurements of the electric and/or magnetic fields. The availability of matrix-factorization software and highperformance computing has allowed us to solve the 3D time domain EM problem using direct solvers. This is particularly advantageous when data from many transmitters and over many decades are available. We first formulate Maxwell’s equations in terms of the magnetic field, ~ H. The problem is then discretized using a finite volume technique in space and backward Euler in time. The forward operator is symmetric positive definite and a Cholesky decomposition can be performed with the work distributed over an array of processors. The forward modeling is quickly carried out using the factored operator. Time savings are considerable and they make 3D inversion of large ground or airborne data sets feasible. This is illustrated by using synthetic examples and by inverting a multisource UTEM field data set acquired at San Nicolas, which is a massive sulfide deposit in Mexico.