Inhibition of subduction thrust earthquakes by low-temperature plastic flow in serpentine

Hirauchi, Ken-ichi; Katayama, Ikuo; Uehara, Satoshi; Miyahara, Masaaki; Takai, Yasuhiro

doi:10.1016/j.epsl.2010.04.007

Cited by 49 publications

(48 citation statements)

References 60 publications

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“…Temperatures in the cold nose (Wada and Wang 2009) match the stability of serpentine (Ulmer and Trommsdorff 1995), the dominant hydrated phase in ultramafic compositions. The low viscosity of serpentine inferred experimentally accounts for the mechanical decoupling of the plate interface at these depths (Amiguet, et al 2012;Chernak and Hirth 2010;Hilairet, et al 2007;Hirauchi, et al 2010).…”

Section: Geophysical Observables and Constrainsmentioning

confidence: 99%

Mantle hydration and Cl-rich fluids in the subduction forearc

Reynard

2016

Prog. in Earth and Planet. Sci.

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In the forearc region, aqueous fluids are released from the subducting slab at a rate depending on its thermal state. Escaping fluids tend to rise vertically unless they meet permeability barriers such as the deformed plate interface or the Moho of the overriding plate. Channeling of fluids along the plate interface and Moho may result in fluid overpressure in the oceanic crust, precipitation of quartz from fluids, and low Poisson ratio areas associated with tremors. Above the subducting plate, the forearc mantle wedge is the place of intense reactions between dehydration fluids from the subducting slab and ultramafic rocks leading to extensive serpentinization. The plate interface is mechanically decoupled, most likely in relation to serpentinization, thereby isolating the forearc mantle wedge from convection as a cold, potentially serpentinized and buoyant, body. Geophysical studies are unique probes to the interactions between fluids and rocks in the forearc mantle, and experimental constrains on rock properties allow inferring fluid migration and fluid-rock reactions from geophysical data. Seismic velocities reveal a high degree of serpentinization of the forearc mantle in hot subduction zones, and little serpentinization in the coldest subduction zones because the warmer the subduction zone, the higher the amount of water released by dehydration of hydrothermally altered oceanic lithosphere. Interpretation of seismic data from petrophysical constrain is limited by complex effects due to anisotropy that needs to be assessed both in the analysis and interpretation of seismic data. Electrical conductivity increases with increasing fluid content and temperature of the subduction. However, the forearc mantle of Northern Cascadia, the hottest subduction zone where extensive serpentinization was first demonstrated, shows only modest electrical conductivity. Electrical conductivity may vary not only with the thermal state of the subduction zone, but also with time for a given thermal state through variations of fluid salinity. High-Cl fluids produced by serpentinization can mix with the source rocks of the volcanic arc and explain geochemical signatures of primitive magma inclusions. Signature of deep high-Cl fluids was also identified in forearc hot springs. These observations suggest the existence of fluid circulations between the forearc mantle and the hot spring hydrothermal system or the volcanic arc. Such circulations are also evidenced by recent magnetotelluric profiles.

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Section: Geophysical Observables and Constrainsmentioning

confidence: 99%

Mantle hydration and Cl-rich fluids in the subduction forearc

Reynard

2016

Prog. in Earth and Planet. Sci.

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“…6 25 MPa, compatible with the small stress drop of slow-slip events and their sensitivity to small external perturbations [69][70][71][72][73] . The low effective normal stress may be caused by high pore pressures associated with the dehydration of the downgoing slab 43,74,75 . Note, however, that our model does not include dynamic dehydration.…”

Section: Semi-brittle Models Of Slow-slip Eventsmentioning

confidence: 99%

“…Furthermore, laboratory friction experiments indicate that serpentine faults are characterized by a low healing rate and a large slip-weakening distance that promotes conditional stability, consistent with the slip mechanism of slow earthquakes 42 . The dominant flow mechanism of antigorite-rich serpentinite shows a transition from semi-brittle (localized) flow by strain localization to ductile (distributed) flow by intracrystalline deformation with increasing temperature from 300 °C to 500 °C at confining pressures from 1 to 2 GPa 43,44 . Serpentinite exhibits nonlinear plastic flow with an effective viscosity much lower than that of the major mantle-forming minerals 38 allowing it to localize deformation.…”

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confidence: 99%

Slow-slip events in semi-brittle serpentinite fault zones

Goswami¹,

Barbot²

2018

Preprint

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Slow-slip events are earthquake-like events only with much lower slip rates. While peak coseismic velocities can reach tens of meters per second, slow-slip is on the order of 10 −7±2 m/s and may last for days to weeks. Under the rate-and-state model of fault friction, slow-slip is produced only when the asperity size is commensurate with the critical nucleation size, a function of frictional properties. However, it is unlikely that all subduction zones embody the same frictional properties. In addition to friction, plastic flow of antigorite-rich serpentinite may significantly influence the dynamics of fault slip near the mantle wedge corner. Here, we show that the range of frictional parameters that generate slow slip is widened in the presence of a serpentinized layer along the subduction plate interface. We observe increased stability and damping of fast ruptures in a semi-brittle fault zone governed by both brittle and viscoelastic constitutive response. The rate of viscous serpentinite flow, governed by dislocation creep, is enhanced by high ambient temperatures. When effective viscosity is taken to be dynamic, long-term slow slip events spontaneously emerge. Integration of rheology, thermal effects, and other microphysical processes with rate-and-state friction may yield further insight into the phenomenology of slow slip.The dynamics of fault slip at subduction zones can assume a wide range of behaviors. A continuum of slip modes that includes fast earthquakes, slow-slip events, and stable creep determines seismic hazards 1,2 . Along the megathrust, earthquakes, very low frequency earthquakes, and tsunami earthquakes are typically found updip of the continental Mohorovicic (Moho) discontinuity. In contrast, slow-slip events are often found close to or below the continental Moho depth at many subduction zones around the circum-Pacific seismic belt 3 , even though some happen at shallow depth, notably in New Zealand 4-6 and Costa Rica 7,8 . Slow-slip events at subduction zones worldwide often embody similar, characteristic features [9][10][11][12][13] . In particular, we observe small stress drops in the range 10-200 kPa, short recurrence times of a few months to a few years, and sometimes more regular periodicity than for earthquakes 14 . Some characteristics of slow-slip events can be explained within the context of rate-and-state friction 15,16 with conditionally stable behavior [17][18][19][20][21] . Runaway frictional instabilities require a critical size for nucleation that depends on the frictional parameters and the effective confining pressure. For sufficiently small velocity-weakening asperities, only creep spontaneously occurs. Slow-slip events emerge spontaneously when the asperity size is commensurate to critical nucleation size 22 . As slow-slip events are now found close to universally at subduction zones [23][24][25][26][27][28] , it is unrealistic to expect the same combination of parameters across widely distant regions (Fig. 1A). Several authors developed and investigated other friction l...

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Section: Starting Materialsmentioning

confidence: 99%

“…These serpentinite samples are from the same stocks used by Hirauchi et al (2010a) and Hirauchi and Katayama (2013) in their highpressure deformation experiments. The rock samples used in the production of the low-T type serpentine mineral powders show mesh texture (Wicks and Whittaker, 1977), consisting of polyhedral, isotropic 'cores' (a mixture of chrysotile nanotubes and magnetite dust) enclosed by fibrous 'rims' (stacks of lizardite crystals) (Hirauchi et al 2010a). The rock samples used in the production of the high-T type serpentine mineral powders exhibit interpenetrating textures (Wicks and Whittaker 1977), comprising 'almost randomly' oriented, platy, or acicular antigorite grains that range from 10 to 150 μm in length, as well as finely disseminated magnetite.…”

Section: Starting Materialsmentioning

confidence: 99%

Effect of stress state on slow rupture propagation in synthetic fault gouges

Hirauchi

Muto

2015

Earth, Planets and Space

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Slow slip events (SSEs) in subduction zones are known to proceed so sluggishly that the associated slow ruptures do not generate any detectable radiating seismic waves. Moreover, they propagate at speeds at least four orders of magnitude slower than regular earthquakes. However, the underlying physics of slow slip generation has yet to be understood. Here, we carry out laboratory studies of unstable slip along simulated fault zones of lizardite/chrysotile (liz/ctl) and antigorite (i.e., low-and high-temperature serpentine phases, respectively) and olivine, under varying conditions of normal stress, with the aim of better understanding the influence of stress state on the process of slow rupture along the plate interface. During a single unstable slip, we clearly observe a slow rupture phase that is often followed by an unstable, high-speed rupture. We find that lower fault-zone friction coefficients (μ values from 0.7 down to 0.5) lead to increasing degree of the slow rupture mode, and also that the slow rupture velocities (V r = 0.07 to 5.43 m/s) are largely consistent with those of short-term SSEs observed in nature. Our findings suggest that the generation of SSEs is facilitated by conditions of low normal stress and low fault-zone strength along the plate interface, which may be weakened by metamorphic reactions that result in the production of hydrous phases (e.g., serpentine) and/or the direct involvement of fluid itself, leading to a reduction in effective normal stress.

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Inhibition of subduction thrust earthquakes by low-temperature plastic flow in serpentine

Cited by 49 publications

References 60 publications

Mantle hydration and Cl-rich fluids in the subduction forearc

Mantle hydration and Cl-rich fluids in the subduction forearc

Slow-slip events in semi-brittle serpentinite fault zones

Effect of stress state on slow rupture propagation in synthetic fault gouges

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