9403925 Zhdanov The PIs will develop algorithms for better imaging, delineation and characterization of underground structures by using electromagnetic geophysical data. The EM migration algorithm is a stable procedure that accurately restores the phase of the upgoing field inside the Earth. It is also computationally efficient compared to previous techniques. The PIs will expand the utility of their present 2D migration method and extend their method to 3D for borehole as well as surface EM data. ****