High-velocity frictional properties of Alpine Fault rocks: Mechanical data, microstructural analysis, and implications for rupture propagation

Boulton, Carolyn, Yao, Lu, Faulkner, Daniel R ORCID: 0000-0002-6750-3775, Townend, John, Toy, Virginia G, Sutherland, Rupert, Ma, Shengli and Shimamoto, Toshihiko (2017) High-velocity frictional properties of Alpine Fault rocks: Mechanical data, microstructural analysis, and implications for rupture propagation. JOURNAL OF STRUCTURAL GEOLOGY, 97. pp. 71-92.

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Abstract

The Alpine Fault in New Zealand is a major plate-bounding structure that typically slips in ∼M8 earthquakes every c. 330 years. To investigate the near-surface, high-velocity frictional behavior of surface- and borehole-derived Alpine Fault gouges and cataclasites, twenty-one rotary shear experiments were conducted at 1 MPa normal stress and 1 m/s equivalent slip velocity under both room-dry and water-saturated (wet) conditions. In the room-dry experiments, the peak friction coefficient (μp = τp/σn) of Alpine Fault cataclasites and fault gouges was consistently high (mean μp = 0.67 ± 0.07). In the wet experiments, the fault gouge peak friction coefficients were lower (mean μp = 0.20 ± 0.12) than the cataclasite peak friction coefficients (mean μp = 0.64 ± 0.04). All fault rocks exhibited very low steady-state friction coefficients (μss) (room-dry experiments mean μss = 0.16 ± 0.05; wet experiments mean μss = 0.09 ± 0.04). Of all the experiments performed, six experiments conducted on wet smectite-bearing principal slip zone (PSZ) fault gouges yielded the lowest peak friction coefficients (μp = 0.10–0.20), the lowest steady-state friction coefficients (μss = 0.03–0.09), and, commonly, the lowest specific fracture energy values (EG = 0.01–0.69 MJ/m2). Microstructures produced during room-dry and wet experiments on a smectite-bearing PSZ fault gouge were compared with microstructures in the same material recovered from the Deep Fault Drilling Project (DFDP-1) drill cores. The near-absence of localized shear bands with a strong crystallographic preferred orientation in the natural samples most resembles microstructures formed during wet experiments. Mechanical data and microstructural observations suggest that Alpine Fault ruptures propagate preferentially through water-saturated smectite-bearing fault gouges that exhibit low peak and steady-state friction coefficients.

Item Type:	Article
Uncontrolled Keywords:	Alpine fault, High-velocity friction, Fracture energy, Rupture propagation, Microstructures, Shear bands
Depositing User:	Symplectic Admin
Date Deposited:	31 Jan 2018 09:00
Last Modified:	19 Jan 2023 06:42
DOI:	10.1016/j.jsg.2017.02.003
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3017210