3-D Imaging of a Planar Interface Close to a Borehole with an Array-Type Directional Borehole Radar

We propose an algorithm for creating a 3-D image of a planar interface with an array-type directional borehole radar. In this paper, we focus on the situation when the radar probe is close to the planar interface. In such circumstances, the reflected wave from the planar interface may be incident on the receiving array antenna at very steep elevation angles. This causes unusual arrival times of the wave at the array elements, and consequently some errors in imaging the planar interface. In our numerical simulation, the proposed algorithm generated a 3-D image of an interface around an exact position whereas a conventional method produced some spurious images opposite the correct position (i.e., off by 180 deg.). We then applied the proposed method to analyze reflected waves from a real-world fault in a rock. Using the proposed algorithm, we could successfully create a 3-D image of the fault, although this was not possible with the conventional method.