Slow slip events are regular earthquakes

Weng, Huihui

doi:10.21203/rs.3.rs-448196/v1

Cited by 2 publications

(2 citation statements)

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“…Using a shear modulus of μ = 30 GPa, we arrive at

K_{normalc}^{drained}

ranging from 0.1 to 1.7 MPa m 1/2 , which overlaps with the K estimate only when very low stress drops are considered in conjunction with large slip weakening distances and effective stress. In addition, rupture events are not expected to be stable if we consider only a balance between K and

K_{normalc}^{drained}

, since any increase in K would lead to dynamic acceleration of the rupture tip (Weng, 2021). When dilatancy is accounted for, ruptures are stabilized since any increase in K and rupture speed can be matched by a corresponding increase in K c (Figure 4; see below).…”

Section: Discussionmentioning

confidence: 99%

Dilatancy Toughening of Shear Cracks and Implications for Slow Rupture Propagation

Brantut

2021

JGR Solid Earth

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Dilatancy is a well documented process in intact, healed or overconsolidated rocks: due to shear deformation, microcavities (cracks, grain junctions) open, which induces an overall increase in porosity (Paterson & Wong, 2005, Section 5.3). In fluid saturated rocks, this increase in porosity has the potential to induce fluid pressure drops if the dilatant region is insufficiently drained, producing an increase in effective stress and thus strengthening the material. This phenomenon is called dilatancy hardening.The importance of dilatancy hardening in fault mechanics has long been recognised in laboratory experiments and in theoretical rupture models. One of the first experimental evidence of dilatancy hardening in crustal rocks was obtained by Brace and Martin (1968) in diabase and granite, who showed that failure strength was increasing with increasing deformation rate as the deformation conditions became more undrained. Similar observations have been made on a range of low-porosity rocks (e.g., Chiu et al., 1983;Duda & Renner, 2013;Rutter, 1972). Martin (1980) further demonstrated that rock failure could be stabilized due to dilatancy, by considerably slowing down the deformation leading to strain localisation and fault slip. New laboratory results by Aben and Brantut (2021) have confirmed the direct stabilization of ruptures due to shear-induced dilation. Such work was focused on initially intact rock, where dilatancy is occurring in the bulk as well as within the incipient fault zone. In preexisting fault zones, dilatancy can be due to overriding asperities (along bare rock surfaces) and granular rearrangements (if gouge layers are present), leading to net fault zone opening during slip. Such behavior has been thoroughly documented in artificial fault gouges, for which dilatancy can be related to frictional state evolution (e.g.,

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“…Using a shear modulus of μ = 30 GPa, we arrive at

K_{normalc}^{drained}

K_{normalc}^{drained}

Section: Discussionmentioning

confidence: 99%

Dilatancy Toughening of Shear Cracks and Implications for Slow Rupture Propagation

Brantut

2021

JGR Solid Earth

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“…Using a shear modulus of μ = 30 GPa, we arrive at 𝐴𝐴 𝐴𝐴 drained c ranging from 0.1 to 1.7 MPa m 1/2 , which overlaps with the K estimate only when very low stress drops are considered in conjunction with large slip weakening distances and effective stress. In addition, rupture events are not expected to be stable if we consider only a balance between K and 𝐴𝐴 𝐴𝐴 drained c , since any increase in K would lead to dynamic acceleration of the rupture tip (Weng, 2021). When dilatancy is accounted for, ruptures are stabilized since any increase in K and rupture speed can be matched by a corresponding increase in K c (Figure 4; see below).…”

mentioning

confidence: 99%

Dilatancy Toughening of Shear Cracks and Implications for Slow Rupture Propagation

Brantut¹

2022

Preprint

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<div> <div> <div> <p>Dilatancy associated with fault slip produces a transient pore pressure drop which increases frictional strength. This effect has been argued to be at least partially at the origin of slow slip events in subduction zones. Recent experimental results have demonstrated that dilatancy hardening has the potential to stabilise rupture in rocks, but laboratory results need to be upscaled to account for large scale variations in slip along faults. Here, we analyze the dilatant hardening in a steadily propagating rupture model that includes frictional weakening, slip-dependent fault dilation and fluid flow. A fracture mechanics approach is used to show that dilatancy hardening tends to increase the stress intensity factor required to propagate the rupture tip. With increasing rupture speed, an undrained (strengthened) region develops near the tip and extends beyond the frictionally weakened zone. Away from the undrained region, pore fluid diffusion gradually recharges the fault and strength returns to the drained, weakened value. For sufficiently large rupture dimensions, the dilation-induced strength increase near the tip is equivalent to an increase in toughness that is proportional to the square root of the rupture speed. In general, dilation has the effect of increasing the stress required for rupture growth by decreasing the stress drop along the crack. The competing effect of thermal pressurization has the potential to compensate for the dilatant strengthening effect, at the expense of an increased heating rate, which might lead to premature frictional melting. Using reasonable laboratory-derived parameters, we show that the dilatancy-toughening effect leads to rupture dynamics that is quantitatively consistent with the dynamics of observed slow slip events in subduction zones.</p> </div> </div> </div>

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Slow slip events are regular earthquakes

Cited by 2 publications

References 54 publications

Dilatancy Toughening of Shear Cracks and Implications for Slow Rupture Propagation

Dilatancy Toughening of Shear Cracks and Implications for Slow Rupture Propagation

Dilatancy Toughening of Shear Cracks and Implications for Slow Rupture Propagation

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