Figure 4. Graph of BO azimuths (red dots), DITF azimuths (blue dots), and stratigraphy column against measured depth (m MD) for boreholes at the southern HSM. Mean BO azimuths and the standard deviation for individual borehole are plotted in black and dashed grey lines respectively. Bi-directional rose diagram of breakout orientations for each borehole is shown below BO panels.
5 Discussion
Our results show that the contemporary SHmaxorientations in the upper plate of the HSM change from dominantly NE-SW, parallel to the subduction margin, within the central HSM to WNW-ESE/NW-SE within the southern HSM (Wairarapa region), roughly perpendicular to the subduction margin (Figure 5). This along-strike rotation in HSM SHmax orientations may be explained in a few ways; 1) HSM kinematics, 2) long-term tectonic deformations, and 3) lateral variations in basement topography.