Loren Mathewson

University of Otago

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C.D. Menzies

Durham University

Martin Zimmer

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

Virginia Toy

University of Otago

Thomas Wiersberg

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

John Townend

Victoria University of Wellington

Osamu Nishikawa

Akita University

Yusuke Kometani

Yamaguchi University

Phædra Upton

GNS Science

Harold Tobin

Earth and Space Research

Cécile Massiot

GNS Science

Cooperative Institutions

Victoria University of Wellington

University of Otago

GNS Science

Centre National de la Recherche Scientifique

International Ocean Discovery Program

Université de Montpellier

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

University of Liverpool

Géosciences Montpellier

University of Southampton

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The origin of fluids and gases in the DFDP-2B borehole, New Zealand; insight from on-line mud gas monitoring

EGU General Assembly Conference Abstracts (2016)

Loren Mathewson Thomas Wiersberg Samuel Niedermann Joerg Erzinger C.D. Menzies

Line (geometry)

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Real Time Mud Gas Logging During Drilling of DFDP-2B

2015 AGU Fall Meeting (2015)

Loren Mathewson Virginia Toy C.D. Menzies Martin Zimmer J. Erzinger

Mud logging

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Bedrock geology of DFDP-2B, central Alpine Fault, New Zealand

Figshare (2017)

Virginia Toy R. Sutherland John Townend Michael J. Allen Leeza Becroft

During the second phase of the Alpine Fault, Deep Fault Drilling Project (DFDP) in the Whataroa River, South Westland, New Zealand, bedrock was encountered in the DFDP-2B borehole from 238.5–893.2 m Measured Depth (MD). Continuous sampling and meso- to microscale characterisation of whole rock cuttings established that, in sequence, the borehole sampled amphibolite facies, Torlesse Composite Terrane-derived schists, protomylonites and mylonites, terminating 200–400 m above an Alpine Fault Principal Slip Zone (PSZ) with a maximum dip of 62°. The most diagnostic structural features of increasing PSZ proximity were the occurrence of shear bands and reduction in mean quartz grain sizes. A change in composition to greater mica:quartz + feldspar, most markedly below c. 700 m MD, is inferred to result from either heterogeneous sampling or a change in lithology related to alteration. Major oxide variations suggest the fault-proximal Alpine Fault alteration zone, as previously defined in DFDP-1 core, was not sampled.

Bedrock

10.6084/m9.figshare.5505199

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Petrophysical, Geochemical, and Hydrological Evidence for Extensive Fracture‐Mediated Fluid and Heat Transport in the Alpine Fault's Hanging‐Wall Damage Zone

Geochemistry Geophysics Geosystems (2017)

John Townend R. Sutherland Virginia Toy Mai‐Linh Doan Bernard Célérier

Abstract Fault rock assemblages reflect interaction between deformation, stress, temperature, fluid, and chemical regimes on distinct spatial and temporal scales at various positions in the crust. Here we interpret measurements made in the hanging‐wall of the Alpine Fault during the second stage of the Deep Fault Drilling Project (DFDP‐2). We present observational evidence for extensive fracturing and high hanging‐wall hydraulic conductivity (∼10 −9 to 10 −7 m/s, corresponding to permeability of ∼10 −16 to 10 −14 m 2 ) extending several hundred meters from the fault's principal slip zone. Mud losses, gas chemistry anomalies, and petrophysical data indicate that a subset of fractures intersected by the borehole are capable of transmitting fluid volumes of several cubic meters on time scales of hours. DFDP‐2 observations and other data suggest that this hydrogeologically active portion of the fault zone in the hanging‐wall is several kilometers wide in the uppermost crust. This finding is consistent with numerical models of earthquake rupture and off‐fault damage. We conclude that the mechanically and hydrogeologically active part of the Alpine Fault is a more dynamic and extensive feature than commonly described in models based on exhumed faults. We propose that the hydrogeologically active damage zone of the Alpine Fault and other large active faults in areas of high topographic relief can be subdivided into an inner zone in which damage is controlled principally by earthquake rupture processes and an outer zone in which damage reflects coseismic shaking, strain accumulation and release on interseismic timescales, and inherited fracturing related to exhumation.

Petrophysics

Earthquake rupture

10.1002/2017gc007202

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Citations (48)

Alpine Fault fluid composition and transport in proximity to the fault, using analyses of out-crop samples and gases entrained in drill fluids

Loren Mathewson

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Petrophysical, geochemical, and hydrological evidence for extensive fracture-mediated fluid and heat transport in the Alpine Fault's hanging-wall damage zone

John Townend R. Sutherland Virginia Toy ML Doan Bernard Célérier

© 2017. American Geophysical Union. All Rights Reserved. Fault rock assemblages reflect interaction between deformation, stress, temperature, fluid, and chemical regimes on distinct spatial and temporal scales at various positions in the crust. Here we interpret measurements made in the hanging-wall of the Alpine Fault during the second stage of the Deep Fault Drilling Project (DFDP-2). We present observational evidence for extensive fracturing and high hanging-wall hydraulic conductivity (∼10−9 to 10−7 m/s, corresponding to permeability of ∼10−16 to 10−14 m2) extending several hundred meters from the fault's principal slip zone. Mud losses, gas chemistry anomalies, and petrophysical data indicate that a subset of fractures intersected by the borehole are capable of transmitting fluid volumes of several cubic meters on time scales of hours. DFDP-2 observations and other data suggest that this hydrogeologically active portion of the fault zone in the hanging-wall is several kilometers wide in the uppermost crust. This finding is consistent with numerical models of earthquake rupture and off-fault damage. We conclude that the mechanically and hydrogeologically active part of the Alpine Fault is a more dynamic and extensive feature than commonly described in models based on exhumed faults. We propose that the hydrogeologically active damage zone of the Alpine Fault and other large active faults in areas of high topographic relief can be subdivided into an inner zone in which damage is controlled principally by earthquake rupture processes and an outer zone in which damage reflects coseismic shaking, strain accumulation and release on interseismic timescales, and inherited fracturing related to exhumation.

Petrophysics

10.26686/wgtn.13876499.v1

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Extreme hydrothermal conditions at an active plate-bounding fault

Nature (2017)

R. Sutherland John Townend Virginia Toy Phædra Upton Jamie Coussens

Hydrostatic pressure

Hydrostatic equilibrium

Heat Generation

Fluid pressure

10.1038/nature22355