oa Determination of Orientation of Horizontal Stress and Localized Rotations of the Orientation Around Faults and Fractures from Breakouts in a Scientific Drilling Borehole

To understand stress perturbations associated with minor faults and fractures, relationships between the faults, fractures, lithologic boundaries and stress changes in hole B of Taiwan Chelungpu-fault Drilling Project (TCDP) were investigated. Here, we reported four patterns of stress changes in the vicinity of faults, fractures and lithologic boundaries found in TCDP hole B: (i) the stress orientation (breakout azimuth) rotates abruptly (discontinuously) in the vicinity of the faults or fractures; (ii) the orientation rotates gradually; (iii) breakouts are suppressed at faults, fractures, or lithologic boundaries; and (iv) the orientation does not change across faults or fractures.