Practical 3D inversion of large airborne time domain electromagnetic data sets

2012 ◽  
Vol 2012 (1) ◽  
pp. 1-4 ◽  
Author(s):  
Dikun Yang ◽  
Douglas W. Oldenburg
Keyword(s):  
Time Domain ◽  
Data Sets ◽  
3D Inversion ◽  
Electromagnetic Data ◽  
Time Domain Electromagnetic

Three dimensional inversion of multisource time domain electromagnetic data

Geophysics ◽  
2013 ◽  
Vol 78 (1) ◽  
pp. E47-E57 ◽  
Author(s):  
Douglas W. Oldenburg ◽  
Eldad Haber ◽  
Roman Shekhtman
Keyword(s):  
Time Domain ◽  
Maxwell’S Equations ◽  
High Performance ◽  
Maxwell's Equations ◽  
Sulfide Deposit ◽  
3D Inversion ◽  
Data Set ◽  
Electromagnetic Data ◽  
Backward Euler ◽  
Time Domain Electromagnetic

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 conductivity-given measurements of the electric and/or magnetic fields. The availability of matrix-factorization software and high-performance 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, [Formula: see text]. 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 Nicolás, which is a massive sulfide deposit in Mexico.

scholarly journals 3D Inversion of Large-scale Time Domain Electromagnetic Data

2013 ◽  
Vol 2013 (1) ◽  
pp. 1-4
Author(s):  
Christoph Schwarzbach ◽  
Elliot Holtham ◽  
Eldad Haber
Keyword(s):  
Time Domain ◽  
Large Scale ◽  
3D Inversion ◽  
Electromagnetic Data ◽  
Time Domain Electromagnetic

Localized S‐inversion of time‐domain electromagnetic data

Geophysics ◽  
2002 ◽  
Vol 67 (4) ◽  
pp. 1115-1125 ◽  
Author(s):  
Michael S. Zhdanov ◽  
Dmitriy A. Pavlov ◽  
Robert G. Ellis
Keyword(s):  
Time Domain ◽  
Thin Sheet ◽  
Data Sets ◽  
Excess Conductance ◽  
Electromagnetic Data ◽  
Time Domain Electromagnetic ◽  
Resistivity Inversion ◽  
And Inversion ◽  
Better Than ◽  
Inhomogeneous Disk

Interpretation of time‐domain electromagnetic (TDEM) data over inhomogeneous geological structures is a challenging problem of geophysical exploration. The most widely used approach of interpreting TDEM data is based on the smooth 1‐D layered resistivity inversion. We have developed an effective technique of fast TDEM inversion based on thin‐sheet conductance approximation that we call S‐inversion. In this paper we extend the S‐inversion technique, approximating the conductivity cross‐section by adding a local inhomogeneous disk with an excess conductance ΔS to the horizontal conductive thin sheet used in S‐inversion. Localized S‐inversion determines the distribution of this excess conductance as a function of a depth and a horizontal coordinate. This new method takes into account the limited horizontal extent of the inhomogeneities, localizing inversion. The numerical modeling results and inversion of practical TDEM data demonstrate that the method resolves local geological targets better than traditional 1‐D inversion and original S‐inversion. The method can be applied to interpret both ground and airborne TDEM data sets.

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