Electromagnetic Geophysical Imaging Incorporating Refraction and Reflection

An accurate technique for remotely determining the internal structure of an object or underground environment would have a significant impact in mining, geoexploration, ultrasonics, and the life sciences. This process of resolving the intrinsic properties of an object or environment by the transmission of radiation or ultrasound through the unknown anomaly is known as reconstructive imaging or tomography. Several efforts have been made to apply imaging (reconstruction) methods to measurements taken between two boreholes on either side of an unknown geophysical structure. However, it became necessary, because of the nature of existing reconstruction methods, to assume a straight-line propagation path from source to receiver. This assumption is not valid in many important applications of geophysical imaging; thus it is desirable to develop a method to account for the radiation mechanisms of re-fraction and reflection in the unknown medium. An imaging scheme that explicitly incorporates refraction and first-order reflection in the reconstruction process is developed. Several examples of successful reconstruction of multicell underground environments are presented to demonstrate its accuracy.