2024-03-29T01:02:48Zhttp://doidb.wdc-terra.org/oaip/oaioai:doidb.wdc-terra.org:63232017-10-15T10:54:22ZDOIDBDOIDB.SDDB
doi:10.5880/ICDP.5052.004
eng
GFZ German Research Centre for Geosciences
http://www.gfz-potsdam.de/
information
pointOfContact
2017-10-09
urn:ogc:def:crs:EPSG:4326
X-ray Computed Tomography and borehole televiewer images of the Alpine Fault’s hanging-wall, New Zealand: Deep Fault Drilling Project phase 1 (DFDP-1) and Amethyst Hydro Project (AHP)
2017-10-09
revision
doi:10.5880/ICDP.5052.004
Williams, Jack
University of Otago, Dunedin, New Zealand
author
Toy, Virginia
University of Otago, Dunedin, New Zealand
author
Massiot, Cecile
GNS Science, New Zealand
author
McNamara, David
National University of Ireland Galway, Ireland
author
The orientations and densities of fractures in the foliated hanging-wall of the Alpine Fault provide insights into the role of a mechanical anisotropy in upper crustal deformation, and the extent to which existing models of fault zone structure can be applied to active plate-boundary faults. Three datasets were used to quantify fracture damage at different distances from the Alpine Fault principal slip zones (PSZs): (1) X-ray computed tomography (CT) images of drill-core collected within 25 m of the PSZs during the first phase of the Deep Fault Drilling Project that were reoriented with respect to borehole televiewer (BHTV) images, (2) field measurements from creek sections at <500 m from the PSZs, and (3) CT images of oriented drill-core collected during the Amethyst Hydro Project at distances of ~500-1400 m from the PSZs.
Results show that within 160 m of the PSZs in foliated cataclasites and ultramylonites, gouge-filled fractures exhibit a wide range of orientations. At these distances, fractures are interpreted to form at high confining pressures and/or in rocks that have a weak mechanical anisotropy. Conversley, at distances greater than 160 m from the PSZs, fractures are typically open and subparallel to the mylonitic foliation or schistosity, implying that fracturing occurred at low confining pressures and/or in rocks that are mechanically anisotropic.
Fracture density is similar across the ~500 m width of the hanging-wall datasets, indicating that the Alpine Fault does not have a typical âdamage zoneâ defined by decreasing fracture density with distance. Instead, we conclude that the ~160 m-wide zone of intensive gouge-filled fractures provides the best estimate for the width of brittle fault-related damage. This estimate is similar to the 60-200 m wide Alpine Fault low-velocity zone detected through fault zone guided waves, indicating that a majority of its brittle damage occurs within its hanging-wall.
The data provided here include CT scan 'core logs' for drill-core from both boreholes of the first phase of the Deep Fault Drilling Project (DFDP-1A and DFDP-1B) and from the Amethyst Hydro Project (AHP), the code to generate 'unrolled' CT images (which is to be run on imageJ), and an overview image of the integration of unrolled DFDP-1B CT images and BHTV images (DFDP-1B_BHTV-CT-Intergration.pdf). The header for the scan log images indicate 'core run-core section-upper depth-lower depth' for DFDP and 'borehole-core run-core section-upper depth-lower depth' for AHP boreholes. CT scan core logs cover the depth range 67.5-91.1 m in DFDP-1A drill-core and all of DFDP-1B drill-core. A classification of fracture type is given in Williams et al (2016). For DFDP-1 CT scan logs, title of each page labelled by: core run - core section - depth range. For AHP CT scan log, header of each page gives: borehole - core run - core section - depth. These are supplementary material to Williams et al. (submitted), in which a methodology for matching unrolled CT and BHTV images is given in Appendix A.
Complete
Williams, Jack
University of Otago, Dunedin, New Zealand
jack.williams@otago.ac.nz
pointOfContact
International Continental Drilling Programme
Alpine Fault
core-log integration
fractures
Deep Fault Drilling Project
DFDP
EARTH SCIENCE > SOLID EARTH > TECTONICS > PLATE TECTONICS > FAULT MOVEMENT
EARTH SCIENCE > SOLID EARTH > ROCKS/MINERALS/CRYSTALS > METAMORPHIC ROCKS > METAMORPHIC ROCK PHYSICAL/OPTICAL PROPERTIES
EARTH SCIENCE > SOLID EARTH > TECTONICS > PLATE TECTONICS > STRESS
NASA/GCMD Earth Science Keywords
publication
CC BY 4.0
CC BY 4.0
10.5194/se-2017-112
DOI
IsSupplementTo
10.1080/00288306.2017.1375533
DOI
References
10.1016/j.jsg.2016.07.006
DOI
References
10.5880/ICDP.5052.005
DOI
HasPart
eng
DFDP-1A: Gaunt Creek, South Westland, New Zealand
170.32550
170.32550
-43.31607
-43.31607
2011-01-18
2011-02-06
DFDP-1B: Gaunt Creek, South Westland, New Zealand
170.32673
170.32673
-43.31602
-43.31602
2011-01-18
2011-02-06
AHP-BH1 Amethyst Hydro Project Borehole 1
170.646911
170.646911
-43.173481
-43.173481
AHP-BH2 Amethyst Hydro Project Borehole 2
170.645885
170.645885
-43.171380
-43.171380
AHP-BH3 Amethyst Hydro Project Borehole 3
170.643860
170.643860
-43.168052
-43.168052
AHP-BH4 Amethyst Hydro Project Borehole 4
170.641756
170.641756
-43.165217
-43.165217
http://dx.doi.org/doi:10.5880/ICDP.5052.004
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