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Joint Seismic And Electrical Tomography
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 10th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems, Mar 1997, cp-204-00040
Abstract
Seismic and electrical properties in the earth are not directly associated with each other. If a large seismic<br>velocity contrast occurs across a geological interface, certain change of the corresponding electrical properties<br>may also take place, but not necessarily. To seek solutions with maximum structure coherency between<br>the two physical parameters in the earth, we develop a joint seismic and electrical tomography method<br>that simultaneously reconstructs seismic velocities and electrical resistivities with cross constraints on the<br>normalized structure curvatures.<br>The joint approach applies a 2D nonlinear refraction traveltime tomography method and a 2.5D d.c.<br>resistivity tomography method in a joint process. It includes a wavefront raytracing method for rapid<br>traveltime calculation, and a transmission-network method for electrical potential calculation. A Conjugate<br>Gradient (CG) approach is applied to solve an inverse problem that minimizes the seismic traveltime and<br>the electrical potential misfits, and meanwhile maximizes coherency of their normalized structure curvatures<br>by the way of Tikhonov regularization.<br>We demonstrate the performance of the joint tomography technique with a numerical example. A geological<br>structure is characterized with three zones in terms of seismic and electrical properties. Applying<br>the joint inversion method takes advantages of both geophysical approaches and automatically reconstructs<br>consistent structures.