Mechanical amorphization, flash heating, and frictional melting: Dramatic changes to fault surfaces during the first millisecond of earthquake slip

Hayward, Kathryn S.; Cox, S. F. J.; Gerald, John Fitz; Slagmolen, B. J. J.; Shaddock, D. A.; Forsyth, P. W. F.; Salmon, M.; Hawkins, Rhys

doi:10.1130/g38242.1

Cited by 34 publications

(40 citation statements)

References 19 publications

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“…This is similar to the findings of Engelder (1976) for sliding on ground surfaces of Westerly granite. Friedman et al (1974) and more recently Hayward et al (2016) reported the occurrence of localized patches bearing small tendrils of glass produced by high-speed frictional melting (e.g., during stick-slip events) in high temperature experiments on sandstones at normal stress conditions overlapping with those used in the present experiments. From microscopic examination of the slip surfaces we did not find any evidence of such occurrences, but this does not preclude the possibility that frictional melting may have developed locally.…”

Section: /2017jb014858mentioning

confidence: 51%

Influence of Normal and Shear Stress on the Hydraulic Transmissivity of Thin Cracks in a Tight Quartz Sandstone, a Granite, and a Shale

Rutter

Mecklenburgh

2018

JGR Solid Earth

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Transmissivity of fluids along fractures in rocks is reduced by increasing normal stress acting across them, demonstrated here through gas flow experiments on Bowland shale, and oil flow experiments on Pennant sandstone and Westerly granite. Additionally, the effect of imposing shear stress at constant normal stress was determined, until frictional sliding started. In all cases, increasing shear stress causes an accelerating reduction of transmissivity by 1 to 3 orders of magnitude as slip initiated, as a result of the formation of wear products that block fluid pathways. Only in the case of granite, and to a lesser extent in the sandstone, was there a minor amount of initial increase of transmissivity prior to the onset of slip. These results cast into doubt the commonly applied presumption that cracks with high resolved shear stresses are the most conductive. In the shale, crack transmissivity is commensurate with matrix permeability, such that shales are expected always to be good seals. For the sandstone and granite, unsheared crack transmissivity was respectively 2 and 2.5 orders of magnitude greater than matrix permeability. For these rocks crack transmissivity can dominate fluid flow in the upper crust, potentially enough to permit maintenance of a hydrostatic fluid pressure gradient in a normal (extensional) faulting regime.

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Section: /2017jb014858mentioning

confidence: 51%

Influence of Normal and Shear Stress on the Hydraulic Transmissivity of Thin Cracks in a Tight Quartz Sandstone, a Granite, and a Shale

Rutter

Mecklenburgh

2018

JGR Solid Earth

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“…This is interpreted to result from either a lower orientation contrast from a nonuniform reflection of low‐loss BSEs in the noncrystalline structure or a reduced Z contrast (representing mean atomic number) due to the lower density of the glass compared with its crystalline equivalent. The amorphous structure of this material has been confirmed using transmission electron microscopy (Hayward et al, ).…”

Section: Resultsmentioning

confidence: 84%

Melt Welding and Its Role in Fault Reactivation and Localization of Fracture Damage in Seismically Active Faults

Hayward

Cox

2017

JGR Solid Earth

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Low displacement fracture damage plays an important role in influencing the behavior and mechanical evolution of faults. Fracture damage zones influence slip behavior through changing near‐field stress orientations, altering fluid pathways and modifying fault structure. Here we use small displacement triaxial experiments to explore the development of fault zone damage, frictional lock‐up, and the generation of new faults using samples with preground faults, oriented in 5° increments between 25° and 65° relative to the shortening direction. With increasing reactivation angle, faults support higher peak normal stresses (104–845 MPa) and behavior transitions from stable sliding to stick slip. Frictional melting occurs on surfaces where stick slip is initiated, forming micron‐thick layers that locally weld asperity contacts. The extent of melt welding is correlated with normal stress and melt‐welded zones increase fault cohesion. Distribution of fracture damage adjacent to the fault is spatially correlated with melt‐welded zones and the corresponding concentrations of stress and elastic strain. In a process referred to as “adhesive wear,” fractures bypassing welded zones transfer melt‐adhered material from one side of the fault to the other, forming new geometric asperities. On faults with high reactivation angles (55°–60°) the increase in cohesive strength resulting from melt‐welded contacts drives fault lock‐up after an initial slip event; subsequent slip localizes on new, favorably oriented faults. Given their size, melt‐welded zones are likely to be short‐lived in nature but may play a significant and previously unrecognized role in the development of fault‐related damage.

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“…The evolution of fault strength during the initial stage of slip plays a crucial role in the fault-weakening processes (Hayward et al, 2016). Indeed, flash melting occurs at the onset of sliding (Beeler et al, 2008;Nielsen et al, 2008;Rice, 2006) for a small amount of slip (Renard et al, 2012), and at highly stressed frictional asperities during rapid slip (Rice, 2006).…”

Section: Surface Melting and Heating Efficiencymentioning

confidence: 99%

Frictional Heating Processes and Energy Budget During Laboratory Earthquakes

Aubry

Passelègue

Deldicque

et al. 2018

Geophysical Research Letters

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During an earthquake, part of the released elastic strain energy is dissipated within the slip zone by frictional and fracturing processes, the rest being radiated away via elastic waves. While frictional heating plays a key role in the energy budget of earthquakes, it could not be resolved by seismological data up to now. Here we investigate the dynamics of laboratory earthquakes by measuring frictional heat dissipated during the propagation of shear instabilities at stress conditions typical of seismogenic depths. We estimate the complete energy budget of earthquake rupture and demonstrate that the radiation efficiency increases with thermal‐frictional weakening. Using carbon properties and Raman spectroscopy, we map spatial heat heterogeneities on the fault surface. We show that an increase in fault strength corresponds to a transition from a weak fault with multiple strong asperities and little overall radiation, to a highly radiative fault behaving as a single strong asperity.

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Mechanical amorphization, flash heating, and frictional melting: Dramatic changes to fault surfaces during the first millisecond of earthquake slip

Cited by 34 publications

References 19 publications

Influence of Normal and Shear Stress on the Hydraulic Transmissivity of Thin Cracks in a Tight Quartz Sandstone, a Granite, and a Shale

Influence of Normal and Shear Stress on the Hydraulic Transmissivity of Thin Cracks in a Tight Quartz Sandstone, a Granite, and a Shale

Melt Welding and Its Role in Fault Reactivation and Localization of Fracture Damage in Seismically Active Faults

Frictional Heating Processes and Energy Budget During Laboratory Earthquakes

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