HR: 11:45h
AN: NG32A-05 INVITED     [Abstracts]
TI: 3-D inversion of controlled source electromagnetic data in active monitoring
AU: * Zhdanov, M
EM: mzhdanov@mines.utah.edu
AF: University of Utah, 135 South 1460 East, Rm 719, Salt Lake City, UT 84112 United States
AB: Electromagnetic (EM) geophysical methods are widely used in active geophysical monitoring. They are based on time-lapse observation and interpretation of the EM fields, periodically excited by the repeated controlled sources. This technology was used for continuous monitoring of the tectonically active zones in different areas of Russia and Japan. The interpretation of the EM monitoring data requires reconstruction of the time-lapse changes in the physical properties of the rocks based on the continuous observations. This problem can be solved by modern methods of EM inversion. In this paper I present a review of the recent developments in the area of rapid 3-D EM forward modeling and inversion. Our approach is based on using a family of linear and nonlinear approximations of EM field, which reduces dramatically the required computational time for both forward modeling and inversion. We have also developed a new integral form of Maxwell's equations allowing for an inhomogeneous background conductivity, which results in a simple, but accurate integral representation for 3-D EM field, similar to the integral formula for the potential field theory. This representation provides an efficient tool for the solution of 3-D EM inverse problems. To obtain a robust inverse model of the conductivity distribution we apply the regularization method based on using a focusing stabilizing functionals (Zhdanov, 2002). The role of these functionals is to select the desired stable solution from a class of solutions with specific physical and/or geometrical properties. One of these properties is the existence of sharp boundaries separating rocks with different petrophysical parameters, e.g., the fault zones. These new stabilizers make it possible to produce clear and focused images of geological targets with sharp boundaries. This new technique can be effectively used for the active EM monitoring of the underground targets.
DE: 0540 Image processing
DE: 0644 Numerical methods
DE: 4499 General or miscellaneous
SC: Nonlinear Geophysics [NG]
MN: Fall Meeting 2005