ur overall goal is to develop efliclent tecnniques t_r high resolution imaging of the electrical structure of the Earth's sut_surtace. We have focussed on natural source techniques, such as magnetotellurics (MT}. The main accomplishment under our past D()E funding has been to implement a new algorithm to invert MT data for multidimensional structure which is orders of magnitude faster and more memory., eflicient than competing algorithms. In our most recent work, we have substantially extended

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... he capability of our two-dimensional cocle: completed basic implementation of a three-dimensional code and investigated holographic techniques able to rapidly extract images without solving for material properties. The pnncipal new goal of our proposed research is to extend our methods to the controlled source electromagnetic (CSEM) techniques used in many industrial applications.