Figure
3. Graph of BO azimuths (red dots), DITF azimuths (blue dots), and
stratigraphy column against measured depth (m MD) for boreholes at the
central 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.
4.2 Southern HSM
A total of 1517 BOs with a combined length of 520 m are identified from
borehole image logs in boreholes Ngapaeruru-1, Rauni-2, Titihaoa-1,
Tawatawa-1, Te Mai-2, and Orui-1A boreholes (Figure 4; data set 1). For
borehole stress data with a WSM quality ranking of B-C (Ngapaeruru-1,
Tawatawa-1, and Ranui-2) we observe an Shmin orientation
of 016°/196° ± 21° (NNE-SSW) from which we infer an
SHmax orientation of 106°/286° (WNW- ESE) (Figure 4).
BOs in boreholes Ngapaeruru-1, Tawatawa-1, Te Mai-2, and the shallow
(<1130 m MD) interval of Ranui-2 show a consistent WNW-ESE
SHmax orientation (Figure 4), whereas BOs measured in
boreholes Titihaoa-1, the deeper (>1130 m MD) imaged
interval of Ranui-2, and Orui-1A provide dominantly NW-SE
SHmax orientations (Figure 4). Our reanalysis of BOs
from borehole Ranui-2 suggest a 51° clockwise SHmaxorientation rotation from E-W (094°/274° ± 17°) in the shallower imaged
depth interval (842-1130 m MD) to NW-SE (145°/325° ± 16°) in the deeper
imaged interval (1130-1422 m MD) (Table 2) that was first reported by
Griffin (2019).
Table 2. Stress
Indicators From Analysis of Borehole Image Logs in the Southern HSM, New
Zealand.