oa Fracture Zone Imaging by Using Radar Yomography - Numerical Study by the Gradient Method

In this paper we show the numerical study of the fracture zone imaging by the radar tomography. The sources are arranged in one bore-hole and the receivers are in another bore-hole. In order to image the conductive distribution between these bore-holes, the gradient method is adopted. It estimates from observed electric field data by using a gradient search for the minimum of error function, and does not require an integral equation or simultaneous equations. The advantage of this inversion scheme is to solve the revised subsurface model quite simply, if we have a forward modeling simulator. The modeling simulator using the Fourie transform based on the FDTD (Finite Difference Time Domain) method is adopted for this simulator since it has the accuracy of the computation results, relatively high speed calculations and small memory space. Numerical studies were carried out and we found that the shape of the fracture zone is recognized clearly after 30 iterations.