What controls the width of ductile shear zones?

Cawood, Tarryn; Platt, J. P.

doi:10.1016/j.tecto.2021.229033

Cited by 13 publications

(8 citation statements)

References 84 publications

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“…In contrast, our model, focusing on longer timescales, is concerned with dilatancy occurring within the much broader damage zone through which along-fault fluid transport occurs. Another conceptual model, which may be relevant below the seismogenic zone, is of a distributed ductile shear zone (Sibson, 1983;Hughes et al, 2020;Cawood & Platt, 2021). In this latter case, the ratio L/w, w being the shear zone width, can be interpreted as the critical strain for porosity evolution.…”

Section: Porosity Permeability and Fluid Equationsmentioning

confidence: 99%

Influence of Creep Compaction and Dilatancy on Earthquake Sequences and Slow Slip

Yang

Dunham

2022

Preprint

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Fluids influence fault zone strength and the occurrence of earthquakes, slow slip events, and aseismic slip. We introduce an earthquake sequence model with fault zone fluid transport, accounting for elastic, viscous, and plastic porosity evolution, with permeability having a power-law dependence on porosity. Fluids, sourced at a constant rate below the seismogenic zone, ascend along the fault. While the modeling is done for a vertical strike-slip fault with 2D antiplane shear deformation, the general behavior and processes are anticipated to apply also to subduction zones. The model produces large earthquakes in the seismogenic zone, whose recurrence interval is controlled in part by compaction-driven pressurization and weakening. The model also produces a complex sequence of slow slip events (SSEs) beneath the seismogenic zone. The SSEs are initiated by compaction-driven pressurization and weakening and stalled by dilatant suctions. Modeled SSE sequences include long-term events lasting from a few months to years and very rapid short-term events lasting for only a few days; slip is ˜1-10 cm. Despite ˜1-10 MPa pore pressure changes, porosity and permeability changes are small and hence fluid flux is relatively constant except in the immediate vicinity of slip fronts. This contrasts with alternative fault valving models that feature much larger changes in permeability from the evolution of pore connectivity. Our model demonstrates the important role that compaction and dilatancy have on fluid pressure and fault slip, with possible relevance to slow slip events in subduction zones and elsewhere.

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Section: Porosity Permeability and Fluid Equationsmentioning

confidence: 99%

Influence of Creep Compaction and Dilatancy on Earthquake Sequences and Slow Slip

Yang

Dunham

2022

Preprint

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“…Either way, during exhumation the analyzed fault rock was brought to the surface, a process that involved cataclasis sensu stricto and lead to the production of a fine and incoherent fault gouge (D4). [75]). BLG-grain bulging, SGR-sub-grain rotation, and GBMgrain boundary migration.…”

Section: Exhumation Historymentioning

confidence: 99%

“…The thin-section analysis reveals that the analysed gouge also contains a certain amount of graphite. Graphite in gouges is not uncommon [27,[77][78][79], and gouges can be [75]). BLG-grain bulging, SGR-sub-grain rotation, and GBM-grain boundary migration.…”

Section: Fault Lubricationmentioning

confidence: 99%

“…Graphite in gouges is not uncommon [27,[77][78][79], and gouges can be composed of crushed quartz and feldspar fragments together with highly crystallized graphite [80]. Similar to phyllosilicates, graphite can also have a lubrication effect, since it is a material with very low friction [63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81]. Experimental studies on mixed graphitequartz gouges indicate strain hardening at low shear strains and/or strain weakening with increasing deformation [82].…”

Section: Fault Lubricationmentioning

confidence: 99%

“…Grey-remnants of folded quartz veins (D1), pink-calcite veining (D4), black lines-D2 foliation and D3 pressure solution planes, green minerals-albite grains. Right; a P-T diagram to summarize the different stages of the fault gouge sample during exhumation (supported by Rings & Merle 1992 [39]; Grasemann and Mancktelow 1993 [33]; Campani et al 2010[36];Bousquet et al, 2002 [74]; Montemagni and Zanchetta[41]; Cawood and Platt 2000[75]). BLG-grain bulging, SGR-sub-grain rotation, and GBM-grain boundary migration.…”

mentioning

confidence: 98%

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The Memory of a Fault Gouge: An Example from the Simplon Fault Zone (Central Alps)

et al. 2022

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A fault gouge forms at the core of the fault as the result of a slip in the upper brittle crust. Therefore, the deformation mechanisms and conditions under which the fault gouge was formed can document the stages of fault movement in the crust. We carried out a microstructural analysis on a fault gouge from a hanging-wall branch fault of the Simplon Fault Zone, a major low-angle normal fault in the Alps. We use thin-section analysis, together with backscattered electron imaging and X-ray diffractometry (XRD), to show that a multistage history from ductile to brittle deformation, together with a continuous exhumation history from high to low temperature, took place within the fault gouge. Because of the predominance of pressure solution and veining, we associated a large part of the deformation in the fault gouge with viscous-frictional behaviour that occurred at the brittle-ductile transition. Phyllosilicates and graphite likely caused fault lubrication that we suggested played a role in the formation of this major low-angle normal fault.

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Intra-channel detachment in a collisional orogen: The Jhala Normal Fault in the Bhagirathi river section, Garhwal Higher Himalaya, India

Bose

Imayama²,

Kawabata³

et al. 2023

J Earth Syst Sci

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What controls the width of ductile shear zones?

Cited by 13 publications

References 84 publications

Influence of Creep Compaction and Dilatancy on Earthquake Sequences and Slow Slip

Influence of Creep Compaction and Dilatancy on Earthquake Sequences and Slow Slip

The Memory of a Fault Gouge: An Example from the Simplon Fault Zone (Central Alps)

Intra-channel detachment in a collisional orogen: The Jhala Normal Fault in the Bhagirathi river section, Garhwal Higher Himalaya, India

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