Application of anisotropy borehole radar tomography in Korea

Although the main geology of Korea consists of granite and gneiss, it is not uncommon to encounter anisotropy phenomena in cross-hole radar tomography even when the basement is crystalline rock. To solve the anisotropy problem, we have developed an anisotropic inversion algorithm, assuming a heterogeneous elliptic anisotropy, to reconstruct three kinds of tomogram: tomograms of maximum and minimum velocities, and of the direction of the symmetry axis. We introduce some case histories of the application of anisotropic radar tomography in Korea. The first two case histories were conducted to construct social infrastructure, and their main objective was to locate cavities in limestone. The last two were performed in a granite and gneiss area. The anisotropy in the granite area was caused by fine fissures aligned in the same direction, while that in the gneiss and limestone areas was caused by the alignment of the constituent minerals. Through these case histories we aim to show that the anisotropic characteristic itself provides additional important information for understanding the internal structure of basement rock.